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                                                    • 1a: Basic Arithmetic
                                                    • 1b: Tree Addressing
                                                    • 1c: Molds and Mold-Builders
                                                    • 2a: Unit Logic
                                                    • 2b: List Logic
                                                    • 2c: Bit Arithmetic
                                                    • 2d: Bit Logic
                                                    • 2e: Insecure Hashing
                                                    • 2f: Noun Ordering
                                                    • 2g: Unsigned Powers
                                                    • 2h: Set Logic
                                                    • 2i: Map Logic
                                                    • 2j: Jar and Jug Logic
                                                    • 2k: Queue Logic
                                                    • 2l: Container from Container
                                                    • 2m: Container from Noun
                                                    • 2n: Functional Hacks
                                                    • 2o: Normalizing Containers
                                                    • 2p: Serialization
                                                    • 2q: Molds and Mold-Builders
                                                    • 3a: Modular and Signed Ints
                                                    • 3b: Floating Point
                                                    • 3c: Urbit Time
                                                    • 3d: SHA Hash Family
                                                    • 3e: AES encryption (Removed)
                                                    • 3f: Scrambling
                                                    • 3g: Molds and Mold-Builders
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                                                    • 4j: Parsing (Bases and Base Digits)
                                                    • 4k: Atom Printing
                                                    • 4l: Atom Parsing
                                                    • 4m: Formatting Functions
                                                    • 4n: Virtualization
                                                    • 4o: Molds
                                                    • 5a: Compiler Utilities
                                                    • 5b: Macro Expansion
                                                    • 5c: Compiler Backend & Prettyprinter
                                                    • 5d: Parser
                                                    • 5e: Molds and mold builders
                                                    • 5f: Profiling support
                                                    • Runes

                                                      • Constants (Atoms and Strings)
                                                      • + lus · Arms
                                                      • | bar · Cores
                                                      • $ buc · Structures
                                                      • % cen · Calls
                                                      • : col · Cells
                                                      • . dot · Nock
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                                                      • --, == Terminators
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                                                                                              Reference/Hoon/Standard Library

                                                                                              2b: List Logic

                                                                                              ++bake

                                                                                              Note: This function isn't specifically a list function but is included in section 2b of the standard library so is documented here for completeness.

                                                                                              Convert wet gate f to a dry gate by specifying argument mold a.

                                                                                              +bake is a wet gate that takes a wet gate and produces a dry gate.

                                                                                              Accepts

                                                                                              f is a gate.

                                                                                              a is a mold.

                                                                                              Produces

                                                                                              A dry gate whose sample type is a.

                                                                                              Source

                                                                                              ++ bake
                                                                                              |* [f=gate a=mold]
                                                                                              |= arg=a
                                                                                              (f arg)

                                                                                              Examples

                                                                                              > =wet-gate |*(a=* [a a])
                                                                                              > (wet-gate 42)
                                                                                              [42 42]
                                                                                              > (wet-gate ['foo' 'bar'])
                                                                                              [['foo' 'bar'] 'foo' 'bar']
                                                                                              > =dry-gate (bake wet-gate @ud)
                                                                                              > (dry-gate 42)
                                                                                              [42 42]
                                                                                              > (dry-gate ['foo' 'bar'])
                                                                                              [email protected]
                                                                                              -have.[@t @t]
                                                                                              nest-fail

                                                                                              ++fand

                                                                                              All indices in list

                                                                                              Produces the indices of all occurrences of nedl in hstk as a list of atoms.

                                                                                              Accepts

                                                                                              nedl is a list.

                                                                                              hstk is a list.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ fand
                                                                                              ~/ %fand
                                                                                              |= [nedl=(list) hstk=(list)]
                                                                                              =| i=@ud
                                                                                              =| fnd=(list @ud)
                                                                                              |- ^+ fnd
                                                                                              =+ [n=nedl h=hstk]
                                                                                              |-
                                                                                              ?: |(?=(~ n) ?=(~ h))
                                                                                              (flop fnd)
                                                                                              ?: =(i.n i.h)
                                                                                              ?~ t.n
                                                                                              ^$(i +(i), hstk +.hstk, fnd [i fnd])
                                                                                              $(n t.n, h t.h)
                                                                                              ^$(i +(i), hstk +.hstk)

                                                                                              Examples

                                                                                              > (fand ~[3] ~[1 2 3])
                                                                                              ~[2]
                                                                                              > (fand ~[4] ~[1 2 3])
                                                                                              ~
                                                                                              > (fand ~['a'] "cbabab")
                                                                                              ~[2 4]
                                                                                              > (fand "ba" "cbabab")
                                                                                              ~[1 3]

                                                                                              ++find

                                                                                              First index in list

                                                                                              Produces the index of the first occurrence of nedl in hstk as the unit of an atom.

                                                                                              Accepts

                                                                                              nedl is a list.

                                                                                              hstk is a list.

                                                                                              Produces

                                                                                              The unit of an atom.

                                                                                              Source

                                                                                              ++ find
                                                                                              ~/ %find
                                                                                              |= [nedl=(list) hstk=(list)]
                                                                                              =| i=@ud
                                                                                              |- ^- (unit @ud)
                                                                                              =+ [n=nedl h=hstk]
                                                                                              |-
                                                                                              ?: |(?=(~ n) ?=(~ h))
                                                                                              ~
                                                                                              ?: =(i.n i.h)
                                                                                              ?~ t.n
                                                                                              `i
                                                                                              $(n t.n, h t.h)
                                                                                              ^$(i +(i), hstk +.hstk)

                                                                                              Examples

                                                                                              > (find [3]~ ~[1 2 3])
                                                                                              [~ u=2]
                                                                                              > (find [4]~ ~[1 2 3])
                                                                                              ~
                                                                                              > (find ['c']~ "cbabab")
                                                                                              [~ u=0]
                                                                                              > (find "ab" "cbabab")
                                                                                              [~ u=2]
                                                                                              > (find "bab" "cbabab")
                                                                                              [~ u=1]

                                                                                              ++flop

                                                                                              Reverse

                                                                                              Produces the list a in reverse order.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ flop
                                                                                              ~/ %flop
                                                                                              |* a=(list)
                                                                                              => .(a (homo a))
                                                                                              ^+ a
                                                                                              =+ b=`_a`~
                                                                                              |-
                                                                                              ?~ a b
                                                                                              $(a t.a, b [i.a b])

                                                                                              Examples

                                                                                              > =a [1 2 3 ~]
                                                                                              > (flop a)
                                                                                              ~[3 2 1]
                                                                                              > (flop (flop a))
                                                                                              ~[1 2 3]

                                                                                              ++gulf

                                                                                              List from range

                                                                                              Produces a list composed of each consecutive integer starting from a and ending with b. a and b are themselves included.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is an atom.

                                                                                              Produces

                                                                                              a list.

                                                                                              Source

                                                                                              ++ gulf
                                                                                              |= [a=@ b=@]
                                                                                              ?> (lte a b)
                                                                                              |- ^- (list @)
                                                                                              ?:(=(a +(b)) ~ [a $(a +(a))])

                                                                                              Examples

                                                                                              > (gulf 1 6)
                                                                                              ~[1 2 3 4 5 6]
                                                                                              > `(list @t)`(gulf 99 106)
                                                                                              <|c d e f g h i j|>

                                                                                              ++homo

                                                                                              Homogenize

                                                                                              Produces a list whose type is a fork of all the contained types in the list a. Used when you want to make all the types of the elements of a list the same.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              Produces

                                                                                              a list.

                                                                                              Source

                                                                                              ++ homo
                                                                                              |* a=(list)
                                                                                              ^+ =< $
                                                                                              |@ ++ $ ?:(*? ~ [i=(snag 0 a) t=$])
                                                                                              --
                                                                                              a

                                                                                              Examples

                                                                                              > lyst
                                                                                              [i=1 t=[i=97 t=[i=2 t=[i=98 t=[i=[~ u=10] t=~]]]]]
                                                                                              > (homo lyst)
                                                                                              ~[1 97 2 98 [~ u=10]]
                                                                                              > =a (limo [1 2 3 ~])
                                                                                              > a
                                                                                              [i=1 t=[i=2 t=[i=3 t=~]]]
                                                                                              > (homo a)
                                                                                              ~[1 2 3]

                                                                                              ++into

                                                                                              Insert item at index

                                                                                              Accepts a list a, an atom b, and a noun c, producing the list of a with the item c inserted at index b.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a atom.

                                                                                              c is a noun.

                                                                                              Produces

                                                                                              the list of a with the item c inserted at index b.

                                                                                              Source

                                                                                              ++ into
                                                                                              ~/ %into
                                                                                              |* [a=(list) b=@ c=*]
                                                                                              ^+ a
                                                                                              (weld (scag b a) [c (slag b a)])

                                                                                              Examples

                                                                                              > (into (limo ~[2 3 4]) 1 11)
                                                                                              ~[2 11 3 4]

                                                                                              ++join

                                                                                              Constructs a new list, placing sep between every element of lit.

                                                                                              Accepts

                                                                                              sep is a noun.

                                                                                              lit is a list.

                                                                                              Produces

                                                                                              a list.

                                                                                              Source

                                                                                              ++ join
                                                                                              |* [sep=* lit=(list)]
                                                                                              =. sep `_?>(?=(^ lit) i.lit)`sep
                                                                                              ?~ lit ~
                                                                                              =| out=(list _?>(?=(^ lit) i.lit))
                                                                                              |- ^+ out
                                                                                              ?~ t.lit
                                                                                              (flop [i.lit out])
                                                                                              $(out [sep i.lit out], lit t.lit)

                                                                                              Examples

                                                                                              > (join ' ' "hoon")
                                                                                              "h o o n"
                                                                                              > (join 0 `(list @)`~[1 2 3])
                                                                                              ~[1 0 2 0 3]

                                                                                              ++lent

                                                                                              List length

                                                                                              Produces the length of any list a as an atom.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              Produces

                                                                                              an atom.

                                                                                              Source

                                                                                              ++ lent
                                                                                              ~/ %lent
                                                                                              |= a=(list)
                                                                                              ^- @
                                                                                              =+ b=0
                                                                                              |-
                                                                                              ?~ a b
                                                                                              $(a t.a, b +(b))

                                                                                              Examples

                                                                                              > (lent [1 2 3 4 ~]))
                                                                                              4
                                                                                              > (lent [1 'a' 2 'b' (some 10) ~])
                                                                                              5

                                                                                              ++levy

                                                                                              Logical "and" on list

                                                                                              Computes the Boolean logical "and" on the results of gate b applied to each individual element in list a.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate.

                                                                                              Produces

                                                                                              A boolean.

                                                                                              Source

                                                                                              ++ levy
                                                                                              ~/ %levy
                                                                                              |* [a=(list) b=$-(* ?)]
                                                                                              |- ^- ?
                                                                                              ?~ a &
                                                                                              ?. (b i.a) |
                                                                                              $(a t.a)

                                                                                              Examples

                                                                                              > =a |=([email protected] (lte a 1))
                                                                                              > (levy `(list @)`[0 1 2 1 ~] a)
                                                                                              %.n
                                                                                              > =a |=([email protected] (lte a 3))
                                                                                              > (levy `(list @)`[0 1 2 1 ~] a)
                                                                                              %.y

                                                                                              ++lien

                                                                                              Logical "or" on list

                                                                                              Computes the Boolean logical "or" on the results of applying gate b to every element of ++list a.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate.

                                                                                              Source

                                                                                              ++ lien
                                                                                              ~/ %lien
                                                                                              |* [a=(list) b=$-(* ?)]
                                                                                              |- ^- ?
                                                                                              ?~ a |
                                                                                              ?: (b i.a) &
                                                                                              $(a t.a)

                                                                                              Examples

                                                                                              > =a |=([email protected] (gte a 1))
                                                                                              > (lien `(list @)`[0 1 2 1 ~] a)
                                                                                              %.y
                                                                                              > =a |=([email protected] (gte a 3))
                                                                                              > (lien `(list @)`[0 1 2 1 ~]) a)
                                                                                              %.n

                                                                                              ++limo

                                                                                              List Constructor

                                                                                              Turns a null-terminated tuple into a list.

                                                                                              Accepts

                                                                                              a is a null-terminated tuple.

                                                                                              Produces

                                                                                              A ++list.

                                                                                              Source

                                                                                              ++ limo
                                                                                              |* a=*
                                                                                              ^+ =< $
                                                                                              |@ ++ $ ?~(a ~ ?:(*? [i=-.a t=$] $(a +.a)))
                                                                                              --
                                                                                              a

                                                                                              Examples

                                                                                              > (limo [1 2 3 ~])
                                                                                              [i=1 t=[i=2 t=[i=3 t=~]]]

                                                                                              ++murn

                                                                                              Maybe transform

                                                                                              Passes each member of list a to gate b, which must produce a unit. Produces a new list with all the results that do not produce ~.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate that produces a unit.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ murn
                                                                                              ~/ %murn
                                                                                              |* [a=(list) b=$-(* (unit))]
                                                                                              => .(a (homo a))
                                                                                              |- ^- (list _?>(?=(^ a) (need (b i.a))))
                                                                                              ?~ a ~
                                                                                              =/ c (b i.a)
                                                                                              ?~ c $(a t.a)
                                                                                              [+.c $(a t.a)]

                                                                                              Examples

                                                                                              > =a |=([email protected] ?.((gte a 2) ~ (some (add a 10))))
                                                                                              > (murn `(list @)`[0 1 2 3 ~] a)
                                                                                              [i=12 t=[i=13 t=~]]

                                                                                              ++oust

                                                                                              Remove

                                                                                              Removes elements from list c beginning at inclusive index a, removing b number of elements.

                                                                                              Accepts

                                                                                              c is a list.

                                                                                              Produces

                                                                                              A ++list.

                                                                                              Source

                                                                                              ++ oust
                                                                                              ~/ %oust
                                                                                              |* [[a=@ b=@] c=(list)]
                                                                                              (weld (scag +<-< c) (slag (add +<-< +<->) c))

                                                                                              Examples

                                                                                              > (oust [4 5] "good day, urbit!")
                                                                                              "good urbit!"
                                                                                              > (oust [2 2] `(list @)`[1 2 3 4 ~])
                                                                                              ~[1 2]

                                                                                              ++reap

                                                                                              Replicate

                                                                                              Replicate: produces a list containing a copies of b.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is a noun.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ reap
                                                                                              ~/ %reap
                                                                                              |* [a=@ b=*]
                                                                                              |- ^- (list _b)
                                                                                              ?~ a ~
                                                                                              [b $(a (dec a))]

                                                                                              Examples

                                                                                              > (reap 20 %a)
                                                                                              ~[%a %a %a %a %a %a %a %a %a %a %a %a %a %a %a %a %a %a %a %a]
                                                                                              > (reap 5 ~s1)
                                                                                              ~[~s1 ~s1 ~s1 ~s1 ~s1]
                                                                                              > `@dr`(roll (reap 5 ~s1) add)
                                                                                              ~s5

                                                                                              ++rear

                                                                                              Last item of list

                                                                                              Produces the last item in list a, crashing if a is null.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              Produces

                                                                                              The type of the last element in a.

                                                                                              Source

                                                                                              ++ rear
                                                                                              ~/ %rear
                                                                                              |* a=(list)
                                                                                              ^- _?>(?=(^ a) i.a)
                                                                                              ?> ?=(^ a)
                                                                                              ?: =(~ t.a) i.a
                                                                                              $(a t.a)

                                                                                              Examples

                                                                                              > (rear ~[1 2 3])
                                                                                              3
                                                                                              > (rear ~)
                                                                                              dojo: hoon expression failed

                                                                                              ++reel

                                                                                              Right fold

                                                                                              Right fold: moves right to left across a list a, recursively slamming a binary gate b with an element from a and an accumulator, producing the final value of the accumulator.

                                                                                              (To "slam" means to call a gate and give it a sample/samples. In this instance, a is the list of samples that are given to the gate b.)

                                                                                              The initial value of the accumulator is the bunt of b's second argument (+<+). This can occasionally produce undesired behavior (see examples). If you need more control over the initial value, try making use of $_ and |:, or perhaps +spin or +spun.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a binary gate.

                                                                                              Produces

                                                                                              The accumulator, which is a noun.

                                                                                              Source

                                                                                              ++ reel
                                                                                              ~/ %reel
                                                                                              |* [a=(list) b=_=>(~ |=([* *] +<+))]
                                                                                              |- ^+ ,.+<+.b
                                                                                              ?~ a
                                                                                              +<+.b
                                                                                              (b i.a $(a t.a))

                                                                                              Examples

                                                                                              > (reel `(list @)`[1 2 3 4 5 ~] add)
                                                                                              15
                                                                                              > (reel `(list @)`[6 3 1 ~] sub)
                                                                                              4
                                                                                              > (reel `(list @)`[3 6 1 ~] sub)
                                                                                              ! subtract-underflow
                                                                                              ! exit

                                                                                              +mul's default sample is 1, so calling +reel with +mul yields the expected behavior:

                                                                                              > *mul
                                                                                              1
                                                                                              > (reel `(list @)`~[1 2 3 4] mul)
                                                                                              24

                                                                                              However, if you build a gate that uses +mul like so, the sample defaults to 0 since that is the bunt of @:

                                                                                              > (reel `(list @)`~[1 2 3 4] |=([[email protected] [email protected]] (mul a b)))
                                                                                              0

                                                                                              We can fix this with |::

                                                                                              > (reel `(list @)`~[1 2 3 4] |:([a=1 b=1] (mul a b)))
                                                                                              24

                                                                                              If you check the definition of +mul, you'll see that it also utilizes this pattern.

                                                                                              We can check explicitly what sequence of operations +reel performs like this:

                                                                                              > =f |: [l='e_l' r='e_r']
                                                                                              ^- @t
                                                                                              :((cury cat 3) '(' l '*' r ')')
                                                                                              > (reel "abcde" f)
                                                                                              '(a*(b*(c*(d*(e*e_r)))))'

                                                                                              ++roll

                                                                                              Left fold

                                                                                              Left fold: moves left to right across a list a, recursively slamming a binary gate b with an element from the list and an accumulator, producing the final value of the accumulator.

                                                                                              (To "slam" means to call a gate and give it a sample/samples. In this instance, a is the list of samples that are given to the gate b.)

                                                                                              The initial value of the accumulator is b's second argument (+<+). This can occasionally produce undesired behavior (see examples). If you need more control over the initial value, try making use of $_ and |:, or perhaps +spin or +spun.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a binary gate.

                                                                                              Produces

                                                                                              The accumulator, which is a noun.

                                                                                              Source

                                                                                              ++ roll
                                                                                              ~/ %roll
                                                                                              |* [a=(list) b=_=>(~ |=([* *] +<+))]
                                                                                              |- ^+ ,.+<+.b
                                                                                              ?~ a
                                                                                              +<+.b
                                                                                              $(a t.a, b b(+<+ (b i.a +<+.b)))

                                                                                              Examples

                                                                                              > (roll `(list @)`[1 2 3 4 5 ~] add)
                                                                                              q=15
                                                                                              > (roll `(list @)`[6 3 1 ~] sub)
                                                                                              ! subtract-underflow
                                                                                              ! exit
                                                                                              > (roll `(list @)`[1 3 6 ~] sub)
                                                                                              q=4

                                                                                              +mul's default sample is 1, so calling +roll with +mul yields the expected behavior:

                                                                                              > *mul
                                                                                              1
                                                                                              > (roll `(list @)`~[1 2 3 4] mul)
                                                                                              24

                                                                                              However, if you build a gate that uses +mul like so, the sample defaults to 0 since that is the bunt of @:

                                                                                              > (roll `(list @)`~[1 2 3 4] |=([[email protected] [email protected]] (mul a b)))
                                                                                              0

                                                                                              We can fix this with |::

                                                                                              > (roll `(list @)`~[1 2 3 4] |:([a=1 b=1] (mul a b)))
                                                                                              24

                                                                                              If you check the definition of +mul, you'll see that it also utilizes this pattern.

                                                                                              We can check explicitly what sequence of operations +roll performs like this:

                                                                                              > =f |: [l='e_l' r='e_r']
                                                                                              ^- @t
                                                                                              :((cury cat 3) '(' l '*' r ')')
                                                                                              > (roll "abcde" f)
                                                                                              '(e*(d*(c*(b*(a*e_r)))))

                                                                                              This is in contrast to what one might expect:

                                                                                              > =foldl
                                                                                              |* [l=(list) f=$-([* *] *)]
                                                                                              ^- f
                                                                                              ?~ l +<-.f
                                                                                              %= $
                                                                                              +<-.f (f +<-.f i.l)
                                                                                              l t.l
                                                                                              ==
                                                                                              > (foldl "abcde" f)
                                                                                              '(((((e_l*a)*b)*c)*d)*e)'

                                                                                              ++scag

                                                                                              Prefix

                                                                                              Accepts an atom a and list b, producing the first a elements of the front of the list.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is a list.

                                                                                              Produces

                                                                                              A list of the same type as b.

                                                                                              Source

                                                                                              ++ scag
                                                                                              ~/ %scag
                                                                                              |* [a=@ b=(list)]
                                                                                              |- ^+ b
                                                                                              ?: |(?=(~ b) =(0 a)) ~
                                                                                              [i.b $(b t.b, a (dec a))]

                                                                                              Examples

                                                                                              > (scag 2 `(list @)`[1 2 3 4 ~])
                                                                                              [i=1 t=~[2]]
                                                                                              > (scag 10 `(list @)`[1 2 3 4 ~])
                                                                                              [i=1 t=~[2 3 4]]

                                                                                              ++skid

                                                                                              Separate

                                                                                              Separates a list a into two lists - Those elements of a who produce true when slammed to gate b and those who produce %.n.

                                                                                              (To "slam" means to call a gate and give it a sample/samples. In this instance, a is the list of samples that are given to the gate b.)

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate that accepts one argument and produces a flag.

                                                                                              Produces

                                                                                              A cell of two lists.

                                                                                              Source

                                                                                              ++ skid
                                                                                              ~/ %skid
                                                                                              |* [a=(list) b=$-(* ?)]
                                                                                              |- ^+ [p=a q=a]
                                                                                              ?~ a [~ ~]
                                                                                              =+ c=$(a t.a)
                                                                                              ?:((b i.a) [[i.a p.c] q.c] [p.c [i.a q.c]])

                                                                                              Examples

                                                                                              > =a |=([email protected] (gth a 1))
                                                                                              > (skid `(list @)`[0 1 2 3 ~] a)
                                                                                              [p=[i=2 t=~[3]] q=[i=0 t=~[1]]]

                                                                                              ++skim

                                                                                              Filter

                                                                                              Cycles through the members of a list a, passing them to a gate b and producing a list of all of the members that produce %.y. Inverse of skip.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate that accepts one argument and produces a boolean.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ skim
                                                                                              ~/ %skim
                                                                                              |* [a=(list) b=$-(* ?)]
                                                                                              |-
                                                                                              ^+ a
                                                                                              ?~ a ~
                                                                                              ?:((b i.a) [i.a $(a t.a)] $(a t.a))

                                                                                              Examples

                                                                                              > =a |=([email protected] (gth a 1))
                                                                                              > (skim `(list @)`[0 1 2 3 ~] a)
                                                                                              [i=2 t=~[3]]

                                                                                              ++skip

                                                                                              Except

                                                                                              Cycles through the members of list a, passing them to a gate b. Produces a list of all of the members that produce %.n. Inverse of skim.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate that accepts one argument and produces a flag.

                                                                                              Produces

                                                                                              A list of the same type as a.

                                                                                              Source

                                                                                              ++ skip
                                                                                              ~/ %skip
                                                                                              |* [a=(list) b=$-(* ?)]
                                                                                              |-
                                                                                              ^+ a
                                                                                              ?~ a ~
                                                                                              ?:((b i.a) $(a t.a) [i.a $(a t.a)])

                                                                                              Examples

                                                                                              > =a |=([email protected] (gth a 1))
                                                                                              > (skip `(l)`[0 1 2 3 ~]) a)
                                                                                              [i=0 t=[i=1 t=~]]

                                                                                              ++slag

                                                                                              Suffix

                                                                                              Accepts an atom a and list b, producing the remaining elements from b starting at a.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is a list.

                                                                                              Produces

                                                                                              A list of the same type as b.

                                                                                              Source

                                                                                              ++ slag
                                                                                              ~/ %slag
                                                                                              |* [a=@ b=(list)]
                                                                                              |- ^+ b
                                                                                              ?: =(0 a) b
                                                                                              ?~ b ~
                                                                                              $(b t.b, a (dec a))

                                                                                              Examples

                                                                                              > (slag 2 (limo [1 2 3 4 ~]))
                                                                                              [i=3 t=[i=4 t=~]]
                                                                                              > (slag 1 (limo [1 2 3 4 ~]))
                                                                                              [i=2 t=[i=3 t=[i=4 t=~]]]

                                                                                              ++snag

                                                                                              Index

                                                                                              Accepts an atom a and a ++list b, producing the element at the index of aand failing if the list is null. Lists are 0-indexed.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is a list.

                                                                                              Produces

                                                                                              Produces an element of b, or crashes if no element exists at that index.

                                                                                              Source

                                                                                              ++ snag
                                                                                              ~/ %snag
                                                                                              |* [a=@ b=(list)]
                                                                                              |- ^+ ?>(?=(^ b) i.b)
                                                                                              ?~ b
                                                                                              ~_ leaf+"snag-fail"
                                                                                              !!
                                                                                              ?: =(0 a) i.b
                                                                                              $(b t.b, a (dec a))

                                                                                              Examples

                                                                                              > (snag 2 "asdf")
                                                                                              'd'
                                                                                              > (snag 0 `(list @ud)`~[1 2 3 4])
                                                                                              1

                                                                                              ++snap

                                                                                              Replace item at index

                                                                                              Accepts a list a, an atom b, and a noun c, producing the list of a with the item at index b replaced with c.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a atom.

                                                                                              c is a noun.

                                                                                              Produces

                                                                                              the list of a with the item at index b replaced with c.

                                                                                              Source

                                                                                              ++ snap
                                                                                              ~/ %snap
                                                                                              |* [a=(list) b=@ c=*]
                                                                                              ^+ a
                                                                                              (weld (scag b a) [c (slag +(b) a)])

                                                                                              Examples

                                                                                              > (snap (limo ~[2 3 4]) 1 11)
                                                                                              ~[2 11 4]

                                                                                              ++snip

                                                                                              Drop tail off list

                                                                                              Removes the last element from list a.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ snip
                                                                                              ~/ %snip
                                                                                              |* a=(list)
                                                                                              ^+ a
                                                                                              ?~ a ~
                                                                                              ?: =(~ t.a) ~
                                                                                              [i.a $(a t.a)]

                                                                                              Examples

                                                                                              > `tape`(snip "foobar")
                                                                                              "fooba"
                                                                                              > (snip ~)
                                                                                              ~

                                                                                              ++snoc

                                                                                              Append

                                                                                              Accepts a ++list a and a noun b, producing the list of b appended to a.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a noun.

                                                                                              Produces

                                                                                              Produces a list of b appended to a.

                                                                                              Source

                                                                                              ++ snoc
                                                                                              |* [a=(list) b=*]
                                                                                              (weld a ^+(a [b]~))

                                                                                              Examples

                                                                                              > `tape`(zing (snoc `(list tape)`~["a" "bc" "def"] "g"))
                                                                                              "abcdefg"
                                                                                              > (snoc `(list @ud)`~[1 2 3] 4)
                                                                                              ~[1 2 3 4]

                                                                                              ++sort

                                                                                              Quicksort

                                                                                              Quicksort: accepts a ++list a and a gate b which accepts two nouns and produces a flag. ++sort then produces a list of the elements of a, sorted according to b.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate that accepts two nouns and produces a boolean.

                                                                                              Produces

                                                                                              A list

                                                                                              Source

                                                                                              ++ sort !.
                                                                                              ~/ %sort
                                                                                              |* [a=(list) b=$-([* *] ?)]
                                                                                              => .(a ^.(homo a))
                                                                                              |- ^+ a
                                                                                              ?~ a ~
                                                                                              =+ s=(skid t.a |:(c=i.a (b c i.a)))
                                                                                              %+ weld
                                                                                              $(a p.s)
                                                                                              ^+ t.a
                                                                                              [i.a $(a q.s)]

                                                                                              Examples

                                                                                              > (sort `(list @)`[0 1 2 3 ~] gth)
                                                                                              ~[3 2 1 0]

                                                                                              ++spin

                                                                                              Gate to list, with state

                                                                                              Accepts a ++list a, some state b, and a gate c. c is called with a tuple -- the head is an element of a and the tail is the state b, and should produce a tuple of the transformed element and the (potentially modified) state b. Produces a pair where the first element is a list of the transformed elements of a, and the second element is the final value of b.

                                                                                              Accepts

                                                                                              a is a ++list.

                                                                                              b is a noun.

                                                                                              c is a gate.

                                                                                              Produces

                                                                                              A pair of a list and a noun.

                                                                                              Source

                                                                                              ++ spin
                                                                                              ~/ %spin
                                                                                              |* [a=(list) b=* c=_|=(^ [** +<+])]
                                                                                              => .(c `$-([_?>(?=(^ a) i.a) _b] [_-:(c) _b])`c)
                                                                                              =/ acc=(list _-:(c)) ~
                                                                                              |- ^- (pair _acc _b)
                                                                                              ?~ a
                                                                                              [(flop acc) b]
                                                                                              =^ res b (c i.a b)
                                                                                              $(acc [res acc], a t.a)

                                                                                              Examples

                                                                                              > %^ spin (limo ~[4 5 6]) :: Trivial example -- does nothing with the state
                                                                                              0
                                                                                              |=([[email protected] [email protected]] [n a])
                                                                                              [p=~[4 5 6] q=0]
                                                                                              > %^ spin (limo ~[4 5 6]) :: Form a pair with `p` as the index and `q` as the list element
                                                                                              0
                                                                                              |=([[email protected] [email protected]] [`(pair)`[a n] +(a)])
                                                                                              [p=~[[p=0 q=4] [p=1 q=5] [p=2 q=6]] q=3]
                                                                                              > %^ spin (reap 10 0) :: Create 10 random numbers less than `10`
                                                                                              ~(. og eny)
                                                                                              |=([[email protected] rng=_og] (rads:rng 10))
                                                                                              [p=~[7 8 6 0 1 5 4 7 9 3] q=<4.rvi {a/@uvJ <51.qyl 129.pdd 41.mac 1.ane $141>}>]

                                                                                              Discussion

                                                                                              (~(rads og eny) 2) creates a random number less than 2, seeding the RNG with entropy (eny). The head of the product is the random number, the tail is the continuation of the RNG.


                                                                                              ++spun

                                                                                              Gate to list, with state

                                                                                              Accepts a list a and a gate b. c is internal state, initially derived by bunting the tail of the sample of gate b, instead of being passed in explicitly as in ++spin. Produces a list with the gate applied to each element of the original list. b is called with a tuple -- the head is an element of a and the tail is the state c, and should produce a tuple of the transformed element and the (potentially modified) state c.

                                                                                              Accepts

                                                                                              a is a ++list.

                                                                                              b is a gate.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ spun
                                                                                              ~/ %spun
                                                                                              |* [a=(list) b=_|=(^ [** +<+])]
                                                                                              p:(spin a +<+.b b)

                                                                                              Examples

                                                                                              > %+ spun (limo ~[4 5 6]) :: `p` as the index and `q` as the list element
                                                                                              |=([[email protected] [email protected]] [`(pair)`[a n] +(a)])
                                                                                              ~[[p=0 q=4] [p=1 q=5] [p=2 q=6]]
                                                                                              > =l (limo ~[7 8 9])
                                                                                              > %+ spun (limo ~[4 5 6]) :: joins two lists into a list of pairs
                                                                                              |=([[email protected] [email protected]] [`(pair)`[(snag a l) n] +(a)])
                                                                                              ~[[p=7 q=4] [p=8 q=5] [p=9 q=6]]

                                                                                              ++swag

                                                                                              Infix

                                                                                              Similar to substr in Javascript: extracts a string infix, beginning at inclusive index a, producing b number of characters.

                                                                                              Accepts

                                                                                              a is an atom.

                                                                                              b is an atom.

                                                                                              c is a list.

                                                                                              Produces

                                                                                              A list of the same type as c.

                                                                                              Source

                                                                                              ++ swag
                                                                                              |* [[a=@ b=@] c=(list)]
                                                                                              (scag +<-> (slag +<-< c))

                                                                                              Examples

                                                                                              > (swag [2 5] "roly poly")
                                                                                              "ly po"
                                                                                              > (swag [2 2] (limo [1 2 3 4 ~]))
                                                                                              [i=3 t=[i=4 t=~]]

                                                                                              ++turn

                                                                                              Gate to list

                                                                                              Accepts a ++list a and a gate b. Produces a list with the gate applied to each element of the original list.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a gate.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ turn
                                                                                              ~/ %turn
                                                                                              |* [a=(list) b=gate]
                                                                                              => .(a (homo a))
                                                                                              ^- (list _?>(?=(^ a) (b i.a)))
                                                                                              |-
                                                                                              ?~ a ~
                                                                                              [i=(b i.a) t=$(a t.a)]

                                                                                              Examples

                                                                                              > (turn (limo [104 111 111 110 ~]) @t)
                                                                                              <|h o o n|>
                                                                                              > =a |=([email protected] (add a 4))
                                                                                              > (turn (limo [1 2 3 4 ~]) a)
                                                                                              ~[5 6 7 8]

                                                                                              Discussion

                                                                                              turn is Hoon's version of 'map' in Haskell.


                                                                                              ++weld

                                                                                              Concatenate

                                                                                              Concatenate two ++lists a and b.

                                                                                              Accepts

                                                                                              a and b are lists.

                                                                                              Source

                                                                                              ++ weld
                                                                                              ~/ %weld
                                                                                              |* [a=(list) b=(list)]
                                                                                              => .(a ^.(homo a), b ^.(homo b))
                                                                                              |- ^+ b
                                                                                              ?~ a b
                                                                                              [i.a $(a t.a)]

                                                                                              Examples

                                                                                              > (weld "urb" "it")
                                                                                              "urbit"
                                                                                              > (weld (limo [1 2 ~]) (limo [3 4 ~]))
                                                                                              ~[1 2 3 4]

                                                                                              ++welp

                                                                                              Perfect weld

                                                                                              Concatenate two ++lists a and b without losing their type information to homogenization.

                                                                                              Accepts

                                                                                              a is a list.

                                                                                              b is a list.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ welp
                                                                                              ~/ %welp
                                                                                              =| [* *]
                                                                                              |@
                                                                                              ++ $
                                                                                              ?~ +<-
                                                                                              +<-(. +<+)
                                                                                              +<-(+ $(+<- +<->))
                                                                                              --

                                                                                              Examples

                                                                                              > (welp "foo" "bar")
                                                                                              "foobar"
                                                                                              > (welp ~[60 61 62] ~[%a %b %c])
                                                                                              [60 61 62 %a %b %c ~]
                                                                                              > ? (welp ~[60 61 62] ~[%a %b %c])
                                                                                              [@ud @ud @ud %a %b %c %~]
                                                                                              [60 61 62 %a %b %c ~]
                                                                                              > (welp [sa+1 so+2 ~] si=3)
                                                                                              [[%sa 1] [%so 2] si=3]

                                                                                              ++zing

                                                                                              Turns a ++list of lists into a single list by promoting the elements of each sublist into the higher.

                                                                                              Accepts

                                                                                              A list of lists.

                                                                                              Produces

                                                                                              A list.

                                                                                              Source

                                                                                              ++ zing
                                                                                              ~/ %zing
                                                                                              =| *
                                                                                              |@
                                                                                              ++ $
                                                                                              ?~ +<
                                                                                              +<
                                                                                              (welp +<- $(+< +<+))
                                                                                              --

                                                                                              Examples

                                                                                              > (zing (limo [(limo ['a' 'b' 'c' ~]) (limo ['e' 'f' 'g' ~]) (limo ['h' 'i' 'j' ~]) ~]))
                                                                                              ~['a' 'b' 'c' 'e' 'f' 'g' 'h' 'i' 'j']
                                                                                              > (zing (limo [(limo [1 'a' 2 'b' ~]) (limo [3 'c' 4 'd' ~]) ~]))
                                                                                              ~[1 97 2 98 3 99 4 100]

                                                                                              <-

                                                                                              2a: Unit Logic

                                                                                              2c: Bit Arithmetic

                                                                                              ->

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                                                                                              Last modified March 17, 2023