Lisp.fif

library Lisp  // tiny Lisp (or rather Scheme) interpreter
"Lists.fif" include
variable lisp-dict
{ hole dup 1 { @ execute } does create } : recursive
{ atom>$ +" undefined" abort } : report-not-found
// a l -- d -1 or a 0  Look up definition d of atom a in dictionary l
{ { dup null? { drop false true }
    { uncons -rot unpair -rot over eq?
      { drop nip true true } { nip swap false } cond
    } cond
  } until
} : lookup-in
// a dict -- def
{ lookup-in ' report-not-found ifnot } : lookup-or-fail
{ lisp-dict @ lookup-or-fail } : lisp-dict-lookup
// a d --  Defines a with definition d in dictionary lisp-dict
{ pair lisp-dict @ cons lisp-dict ! } : lisp-dict-int-define
{ box lisp-dict-int-define } : lisp-dict-define
// a d -- Defines new a with defininition d
{ over lisp-dict @ lookup-in { 2drop atom>$ +" already defined" abort }
  { drop lisp-dict-int-define } cond
} : lisp-dict-int-define-new
{ box lisp-dict-int-define-new } : lisp-dict-define-new
// a e -- Defines a with executable definition given by e
{ single lisp-dict-define-new } : lisp-dict-define-exec
// expr ctx def -- val
{ dup first execute } : run-definition
// expr ctx -- val
recursive lisp-ctx-eval {
  over tuple?
  { over first over lisp-ctx-eval run-definition }
  { over atom? { lookup-or-fail @ } { drop } cond }
  cond
} swap !
// exp -- value
{ lisp-dict @ lisp-ctx-eval } : lisp-eval
// (exprs) ctx -- (vals)
recursive lisp-ctx-eval-list
{ over null? { drop } {
  swap uncons -rot over lisp-ctx-eval -rot lisp-ctx-eval-list cons
  } cond
} swap !
// (exprs) ctx -- val
{ null rot {
  dup null? { drop nip true } {
  nip uncons swap 2 pick lisp-ctx-eval swap false
  } cond } until
} : lisp-ctx-eval-list-last
// l c -- (args)
{ swap uncons nip swap lisp-ctx-eval-list } : extract-eval-arg-list
{ drop uncons nip } : extract-arg-list
// (x1 .. xn) e n -- x1 .. xn e
{ { swap uncons rot } swap times
  swap null? not abort"invalid number of arguments"
} : unpack-list
// l c n e -- v
{ swap 2swap extract-eval-arg-list  // e n (args)
  -rot unpack-list execute
} : eval-exec-fixed
// l c n e -- v
{ 2 pick pair
  swap 2swap extract-arg-list  // [e c] n (args)
  -rot unpack-list unpair swap execute
} : exec-fixed
// l c e -- v
{ -rot extract-eval-arg-list  // e (args)
  swap execute
} : eval-exec-list
{ -rot tuck extract-arg-list  // e c (args)
  swap rot execute
} : exec-list
// e a n --
{ rot 2 {  // expr ctx def n e
    rot drop eval-exec-fixed } does
  lisp-dict-define-exec
} : lisp-fixed-primitive
{ rot 2 { rot drop exec-fixed } does lisp-dict-define-exec
} : lisp-fixed-lazy-primitive
// e a --
{ swap 1 { nip eval-exec-list } does lisp-dict-define-exec
} : lisp-primitive
{ swap 1 { nip exec-list } does lisp-dict-define-exec
} : lisp-lazy-primitive

// Uncomment next line for Fift booleans
// false constant #f  true constant #t  null constant no-answer
// Uncomment next line for Scheme booleans
`#f constant #f  `#t constant #t  #f constant no-answer
{ #f eq? } : lisp-false?
{ lisp-false? 0= } : lisp-true?
{ ' #t ' #f cond } : lisp-bool

// temp for defining a lot of primitives
{ bl word atom lisp-primitive } : L:
{ bl word atom swap lisp-dict-define } : L=:
{ bl word atom swap lisp-fixed-primitive } : #L:
{ 0 #L: } : 0L:
{ 1 #L: } : 1L:
{ 2 #L: } : 2L:

// basic primitives
{ sum-list } L: +
{ - } 2L: -
{ dup null? { drop 1 } { ' * foldl-ne } cond } L: *
{ / } 2L: /
{ mod } 2L: modulo
{ abs } 1L: abs
{ ' min foldl-ne } L: min
{ ' max foldl-ne } L: max
{ true ' and foldl } L: integer-and
{ false ' or foldl } L: integer-or
{ 0 ' xor foldl } L: integer-xor
{ not } 1L: integer-not
{ = lisp-bool } 2L: =
{ <> lisp-bool } 2L: <>
{ < lisp-bool } 2L: <
{ <= lisp-bool } 2L: <=
{ > lisp-bool } 2L: >
{ >= lisp-bool } 2L: >=
{ eq? lisp-bool } 2L: eq?
{ eqv? lisp-bool } 2L: eqv?
{ equal? lisp-bool } 2L: equal?
{ cons } 2L: cons
{ car } 1L: car
{ cdr } 1L: cdr
{ cadr } 1L: cadr
{ cddr } 1L: cddr
{ caddr } 1L: caddr
{ cdr cddr } 1L: cdddr
{ concat-list-lists } L: append
{ list-reverse } 1L: reverse
{ list-tail } 2L: list-tail
{ list-ref } 2L: list-ref
{ list-member-eq } 2L: memq
{ list-member-eqv } 2L: memv
{ list-member-equal } 2L: member
{ assq ' #f ifnot } 2L: assq
{ assv ' #f ifnot } 2L: assv
{ assoc ' #f ifnot } 2L: assoc
{ list? lisp-bool } 1L: list?
{ pair? lisp-bool } 1L: pair?
{ tuple? lisp-bool } 1L: tuple?
{ string? lisp-bool } 1L: string?
{ integer? lisp-bool } 1L: integer?
{ integer? lisp-bool } 1L: number?
{ count } 1L: width
{ list-length } 1L: length
{ [] } 2L: tuple-ref
{ first } 1L: first
{ second } 1L: second
{ third } 1L: third
{ 3 [] } 1L: fourth
{ list>tuple } 1L: list->tuple
{ explode list } 1L: tuple->list
null L=: null
{ atom? lisp-bool } 1L: symbol?
{ atom } 1L: string->symbol
{ atom>$ } 1L: symbol->string
{ dup #f eq? swap #t eq? or lisp-bool } 1L: boolean?
#t L=: else
#f L=: #f
#t L=: #t
{ null? lisp-bool } 1L: null?
{ 0= lisp-bool } 1L: zero?
{ 0> lisp-bool } 1L: positive?
{ 0< lisp-bool } 1L: negative?
{ 1 and 0= lisp-bool } 1L: even?
{ 1 and 0<> lisp-bool } 1L: odd?
{ bye } 0L: exit
{ .l null } 1L: write
{ lisp-eval } 1L: eval
{ drop } `quote 1 lisp-fixed-lazy-primitive
'nop L: list
{ list>tuple } L: tuple
{ list-last } L: begin
{ $len } 1L: string-length
{ concat-string-list } L: string-append
{ $= lisp-bool } 2L: string=?
{ $cmp 0< lisp-bool } 2L: string<?
{ $cmp 0<= lisp-bool } 2L: string<=?
{ $cmp 0> lisp-bool } 2L: string>?
{ $cmp 0>= lisp-bool } 2L: string>=?
{ (number) dup 1 = { drop } { ' 2drop if no-answer } cond
} 1L: string->number
{ (.) } 1L: number->string
{ box? lisp-bool } 1L: box?
{ box } 1L: box
{ hole } 0L: new-box
{ @ } 1L: unbox
{ tuck swap ! } 2L: set-box!
{ abort } 1L: error
{ dup find { nip execute } { +" -?" abort } cond } : find-execute
{ explode-list 1- roll find-execute } L: fift-exec
{ explode-list dup 1- swap roll find-execute } L: fift-exec-cnt
{ uncons swap find-execute } L: fift-exec-list
// end of basic primitives
forget L:  forget #L:  forget L=:
forget 0L:  forget 1L:  forget 2L:

{ { dup tuple? ' do-quote if } list-map } : map-quote
{ uncons ' cons foldr-ne map-quote
  null swap cons lisp-dict @ rot run-definition
} `apply lisp-primitive  // bad: should have preserved original context
// e1 e2 e3 ctx
{ 3 exch 3 pick lisp-ctx-eval lisp-true? ' swap if nip swap lisp-ctx-eval }
`if 3 lisp-fixed-lazy-primitive
// (e) ctx
{ #t -rot
  { over null? { 2drop true } {
    swap uncons swap 2 pick lisp-ctx-eval dup lisp-true? // v' c t v ?
    { swap 2swap nip false } { -rot 2drop nip true } cond
  } cond } until
} `and lisp-lazy-primitive
{ #f -rot
  { over null? { 2drop true } {
    swap uncons swap 2 pick lisp-ctx-eval dup lisp-false? // v' c t v ?
    { swap 2swap nip false } { -rot 2drop nip true } cond
  } cond } until
} `or lisp-lazy-primitive
{ lisp-false? lisp-bool } `not 1 lisp-fixed-primitive
// cond-clause ctx -- v -1 or 0
{ swap uncons -rot dup `else eq? {
  drop lisp-ctx-eval-list-last true } {
  over lisp-ctx-eval lisp-true? {
  lisp-ctx-eval-list-last true } {
  2drop false
  } cond } cond
} : eval-cond-clause
// (clauses) ctx -- v
{ { over null? { no-answer true } {
    swap uncons -rot over eval-cond-clause } cond
  } until -rot 2drop
} `cond lisp-lazy-primitive
{ lisp-dict @ lookup-in { hole tuck lisp-dict-int-define } ifnot
} : lisp-create-global-var
// a e ctx  -- old (simple) define
{ drop over atom? not abort"only a variable can be define'd"
  over lisp-create-global-var swap lisp-eval swap !
} drop // `define 2 lisp-fixed-lazy-primitive
{ tuck lisp-ctx-eval rot dup atom? not abort"only a variable can be set"
  rot lookup-or-fail dup @ -rot !
} `set! 2 lisp-fixed-lazy-primitive
// define lambda
{ { dup null? { drop true true }
    { uncons swap atom? { false } { drop false true } cond } cond
  } until
} : var-list?
{ { dup null? over atom? or { drop true true }
    { uncons swap atom? { false } { drop false true } cond } cond
  } until
} : lambda-var-list?
// (quote x) -- x -1 ; else 0
{ dup pair? { uncons swap `quote eq? { car true } { drop false } cond }
  { drop false } cond
} : is-quote?
recursive match-arg-list-acc
// l (vars) (args) -- ((var . arg) ...)+l -1 or ? 0
{ over atom? { over `_ eq? { 2drop } { pair swap cons } cond true } {
  over null? { nip null? } { // (vars) (args)
  over tuple? not { 2drop false } {
  over is-quote? { eq? nip } { // (v) (a)
  dup tuple? not { 2drop false } {
  over count over count over <> { drop 2drop false } { // l [v] [a] n
  3 roll 0 rot { // [v] [a] l i
    dup 0< {
      3 pick over [] swap  // [v] [a] l vi i
      3 pick over [] 2swap rot // [v] [a] i l vi ai
      match-arg-list-acc { // [v] [a] i l'
        swap 1+ } { nip -1 } cond
    } ifnot
  } swap times
  2swap 2drop 0>=
  } cond } cond } cond } cond } cond } cond
} swap !
{ null -rot match-arg-list-acc } : match-arg-list
// ((var . arg)...) ctx -- ctx'
{ { over null? not }
  { swap uncons swap unpair box pair rot cons } while
  nip
} : extend-ctx-by-list
// ((vars) body) ctx
{ swap uncons -rot
  dup lambda-var-list? not abort"invalid formal parameter list"
  { // l-expr ctx' [_ body ctx (vars)]
    -rot 2 pick 3 [] swap rot  // [_ body ...] (vars) ctx' l-expr
    uncons nip swap lisp-ctx-eval-list  // [_ body ...] (vars) (arg-vals)
    match-arg-list not abort"invalid arguments to lambda" // [_ body ...] ((var arg)...)
    over third extend-ctx-by-list // [_ body ctx (vars)] ctx''
    swap second swap lisp-ctx-eval-list-last
  } 3 -roll 4 tuple
} : make-lambda
{ make-lambda } `lambda lisp-lazy-primitive
// (a e) ctx -- more sophisticated (define a e)
{ drop uncons swap dup atom? { // (e) a
    tuck lisp-create-global-var
    swap lisp-dict @ lisp-ctx-eval-list-last swap !
  } { // (e) (a v..)
    uncons over atom? not abort"only variables can be define'd"  // (e) a (v..)
    rot cons over lisp-create-global-var   // a ((v..) (e)) h
    swap lisp-dict @ make-lambda swap !
  } cond
} `define lisp-lazy-primitive
// ((x e) ..) ctx -- ((x.v) ..)
recursive eval-assign-list
{ over null? { drop } {
  swap uncons swap uncons // ctx t x (e)
  over atom? not abort"invalid variable name in assignment list"
  3 pick lisp-ctx-eval-list-last  // ctx t x v
  pair swap rot eval-assign-list cons
  } cond
} swap !
// (((x v) ..) body) ctx  -- let construct
{ swap uncons swap 2 pick eval-assign-list  // ctx body ((x v)...)
  rot extend-ctx-by-list lisp-ctx-eval-list-last
} `let lisp-lazy-primitive
// ((x e) ..) ctx -- ctx'
{ swap {
  dup null? { drop true } {
  uncons swap uncons  // ctx t x (e)
  over atom? not abort"invalid variable name in assignment list"
  3 pick lisp-ctx-eval-list-last  // ctx t x v
  box pair rot cons swap false
  } cond } until
} : compute-let*-ctx
// (((x v) ..) body) ctx  -- let* construct
{ swap uncons swap rot compute-let*-ctx lisp-ctx-eval-list-last
} `let* lisp-lazy-primitive
// ((x e) ..) ctx -- ((h e) ..) ctx' , with x bound to h in ctx'
recursive prepare-letrec-ctx {
  over null? {
  swap uncons swap uncons swap // ctx t (e) x
  hole tuck pair swap rot cons // ctx t (x.h) (h e)
  3 -roll rot cons prepare-letrec-ctx // (h e) t ctx'
  -rot cons swap
  } ifnot
} swap !
// (((x v) ..) body) ctx  -- letrec construct
{ swap uncons swap rot prepare-letrec-ctx swap { // body ctx' ((h e)..)
    dup null? { drop true } {
    uncons -rot uncons 2 pick lisp-ctx-eval-list-last // body t ctx' h v
    swap ! swap false
  } cond } until
  lisp-ctx-eval-list-last
} `letrec lisp-lazy-primitive
// (e (p e)...) ctx -- match construct
{ swap uncons swap 2 pick lisp-ctx-eval swap { // ctx v ((p e)..)
  dup null? { drop 2drop no-answer true } {
  uncons swap uncons swap 3 pick // ctx v t e p v
  match-arg-list { // ctx v t e ((x' . v')...)
  2swap 2drop rot extend-ctx-by-list lisp-ctx-eval-list-last true } {
  2drop false
  } cond } cond } until
} `match lisp-lazy-primitive
//
lisp-dict @ constant original-lisp-dict
{ original-lisp-dict lisp-dict ! } : reset-lisp
{ ' drop { lisp-eval .l cr } List-generic( } :_ LISP-EVAL-PRINT(
// LISP-EVAL-PRINT((+ 3 4) (* 5 6)) computes and prints 12 and 30
{ hole dup 1 { @ nip } does swap
  1 { swap lisp-eval swap ! } does
  List-generic(
} :_ LISP-EVAL(
// LISP-EVAL((+ 3 4) (* 5 6)) computes 12 and 30, returns only 30

// words for invoking Lisp definitions from Fift
// (args) def -- val
{ null rot map-quote cons lisp-dict @ rot run-definition
} : invoke-lisp-definition
{ atom lisp-dict-lookup 1 { @ invoke-lisp-definition }
} : (invoke-lisp)
{ bl word (invoke-lisp) } :: invoke-lisp
// ( 2 3 ) invoke-lisp compare .l
{ atom lisp-dict-lookup 2 { @ mklist-1 invoke-lisp-definition }
} : (invoke-lisp-fixed)
{ bl word (invoke-lisp-fixed) } :: invoke-lisp-fixed
// 9 8  2 invoke-lisp-fixed compare .l
{ bl word (invoke-lisp) does } : make-lisp-invoker
{ bl word (invoke-lisp-fixed) does } : make-lisp-fixed-invoker
// 2 make-lisp-fixed-invoker compare : compare
// 3 9 compare
// import Lisp definitions as Fift words
{ bl word dup (invoke-lisp) does swap 0 (create) } : import-lisp
{ bl word tuck (invoke-lisp-fixed) does swap 0 (create) } : import-lisp-fixed
// 1 import-lisp-fixed fact
// 7 fact .