gk

This is an implementation of the k programming language, originally invented by Arthur Whitney.

It's loosely based on k3, but with some changes suggested by Stevan Apter.

Some other notable open source implementations of k:

build instructions

linux/mac:

make
make test

win: (requires visual studio cli)

make.bat

gk differences from k3

verbs

The verbs are all like k3. However, there is no "force monadic" (ex: #:'). The valence of primitive verbs (including composition) is always determined from context. A few examples:

  #'(1 2;3 4 5)
2 3
  !'2 3 4
(0 1
 0 1 2
 0 1 2 3)
  *'("ab";"cd";"ef")
"ace"
  (%-)'1 2 3
-1 -0.5 -0.3333333

adverbs

The adverbs are similar to k3, but /: \: ': are gone. The only adeverbs are / \ '. How they operate depends on the context and the valence of the modified verb. Here's a quick synopsis:

      monad: each      f'x
       dyad: eachprior f'x
 infix dyad: slide     n f'x
prefix dyad: each      f'[x;y]
      other: each      f'[x;y;z]

      monad: scanm     f\x
      monad: do        n f\x
      monad: while     b f\x
 infix dyad: eachleft  x f\y
prefix dyad: scand     f\x
      other: scan      f\[x;y;z]

      monad: overm     f/x
      monad: do        n f/x
      monad: while     b f/x
 infix dyad: eachright x f/y
prefix dyad: overd     f/x
      other: over      f/[x;y;z]

slide adverb

The slide adverb is an enhanced version of eachpair (aka eachprior). It only takes effect in the context of infix notation.

The left argument is a positive or negative integer. Its sign indicates the order the arguments are passed to the modified verb. Its absolute value indicates the number of steps the sliding window moves each time arguments are taken. These examples should make clear how it works:

  1 ,' "abcd"
("ab"
 "bc"
 "cd")
  -1 ,' "abcd"
("ba"
 "cb"
 "dc")
  2 ,' "abcd"
("ab"
 "cd")
  -2 ,' "abcd"
("ba"
 "dc")

So -1 f' a in gk is equivalent to f': a in k3. gk gives up the k3 behavior of prepending the left argument of eachprior to the result in order to have a much more flexible adverb.

I believe its a good tradeoff since I've never found a good use for something like this in k3:

  `a-':1 2 3
(`a;1;1)

However, you can still do that in gk if you need to for some reason. Ex:

  `a,-1-'1 2 3
(`a;1;1)

no underscore in names

Underscores are not allowed in variable names. It makes things cleaner since there is no longer a need to have space around the drop/cut verb.

  a:1
  b:1 2 3
  a_b
2 3

Most of the reserved names from k3 are still there, but with the _ removed.

  draw[10;10]
7 2 7 6 6 3 6 2 5 8
  1 2 3 dv 2
1 3
  2 vs 5
1 0 1

I didn't want to reserve single-letter names, so some have changed.

k3     gk
---    ----
 _n    nul
 _P    .z.P
 _T    .z.T
 _f    .z.f
 _h    .z.h
 _i    .z.i
 _t    .z.t

$ replaces : in cond

  a:0;$[a;`a;`b]
`b
  a:1;$[a;`a;`b]
`a

cmh25 / gk

gk