4 include term-colours.4th
10 1 constant boolean-type
11 2 constant character-type
12 3 constant string-type
15 6 constant symbol-type
16 : istype? ( obj type -- obj bool )
19 \ ------ Cons cell memory ------ {{{
22 create car-cells N allot
23 create car-type-cells N allot
24 create cdr-cells N allot
25 create cdr-type-cells N allot
30 : cons ( car-obj cdr-obj -- pair-obj )
31 cdr-type-cells nextfree @ + !
32 cdr-cells nextfree @ + !
33 car-type-cells nextfree @ + !
34 car-cells nextfree @ + !
41 : car ( pair-obj -- car-obj )
43 dup car-cells + @ swap
47 : cdr ( pair-obj -- car-obj )
49 dup cdr-cells + @ swap
53 : set-car! ( obj pair-obj -- )
55 rot swap car-type-cells + !
59 : set-cdr! ( obj pair-obj -- )
61 rot swap cdr-type-cells + !
71 : nil? nil-type istype? ;
73 : objvar create nil swap , , ;
75 : value@ ( objvar -- val ) @ ;
76 : type@ ( objvar -- type ) 1+ @ ;
77 : value! ( newval objvar -- ) ! ;
78 : type! ( newtype objvar -- ) 1+ ! ;
79 : setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ;
80 : fetchobj ( objvar -- obj ) dup @ swap 1+ @ ;
82 : objeq? ( obj obj -- bool )
87 \ ---- Pre-defined symbols ---- {{{
91 : (create-symbol) ( addr n -- symbol-obj )
95 2dup drop @ character-type 2swap
103 : create-symbol ( -- )
112 symbol-table fetchobj
117 does> dup @ swap 1+ @
120 create-symbol quote quote-symbol
121 create-symbol define define-symbol
122 create-symbol set! set!-symbol
123 create-symbol ok ok-symbol
127 \ ---- Environments ---- {{{
131 : enclosing-env ( env -- env )
134 : first-frame ( env -- frame )
137 : make-frame ( vars vals -- frame )
140 : frame-vars ( frame -- vars )
143 : frame-vals ( frame -- vals )
146 : add-binding ( var val frame -- )
147 2swap 2over frame-vals cons
149 2swap 2over frame-vars cons
153 : extend-env ( vars vals env -- env )
163 : get-vars-vals-frame ( var frame -- bool )
164 2dup frame-vars vars setobj
165 frame-vals vals setobj
168 vars fetchobj nil objeq? false =
170 2dup vars fetchobj car objeq? if
175 vars fetchobj cdr vars setobj
176 vals fetchobj cdr vals setobj
182 : get-vars-vals ( var env -- vars? vals? bool )
185 2dup nil objeq? false =
187 2over 2over first-frame
188 get-vars-vals-frame if
190 vars fetchobj vals fetchobj true
204 : lookup-var ( var env -- val )
208 bold fg red ." Tried to read unbound variable." reset-term abort
212 : set-var ( var val env -- )
213 >R >R 2swap R> R> ( val var env )
215 2swap 2drop ( val vals )
218 bold fg red ." Tried to set unbound variable." reset-term abort
224 : define-var ( var val env -- )
227 2over env fetchobj ( var val var env )
229 2swap 2drop ( var val vals )
234 first-frame ( var val frame )
246 variable stored-parse-idx
247 create parse-str 161 allot
248 variable parse-str-span
250 create parse-idx-stack 10 allot
251 variable parse-idx-sp
252 parse-idx-stack parse-idx-sp !
255 parse-idx @ parse-idx-sp @ !
260 parse-idx-sp @ parse-idx-stack <= abort" Parse index stack underflow."
264 parse-idx-sp @ @ parse-idx ! ;
268 '\n' parse-str parse-str-span @ + !
269 1 parse-str-span +! ;
276 parse-str 160 expect cr
277 span @ parse-str-span !
287 : charavailable? ( -- bool )
288 parse-str-span @ parse-idx @ > ;
290 : nextchar ( -- char )
291 charavailable? false = if getline then
292 parse-str parse-idx @ + @ ;
294 : whitespace? ( -- bool )
303 nextchar [char] ( = or
304 nextchar [char] ) = or
321 nextchar [char] - = ;
323 : number? ( -- bool )
324 digit? minus? or false = if
345 : boolean? ( -- bool )
346 nextchar [char] # <> if false exit then
353 and if pop-parse-idx false exit then
365 : str-equiv? ( str -- bool )
382 delim? false = if drop false then
387 : character? ( -- bool )
388 nextchar [char] # <> if false exit then
393 nextchar [char] \ <> if pop-parse-idx false exit then
397 S" newline" str-equiv? if pop-parse-idx true exit then
398 S" space" str-equiv? if pop-parse-idx true exit then
399 S" tab" str-equiv? if pop-parse-idx true exit then
401 charavailable? false = if pop-parse-idx false exit then
407 nextchar [char] ( = ;
409 : string? ( -- bool )
410 nextchar [char] " = ;
412 : readnum ( -- num-atom )
420 10 * nextchar [char] 0 - +
429 : readbool ( -- bool-atom )
432 nextchar [char] f = if
443 : readchar ( -- char-atom )
447 S" newline" str-equiv? if 7 parse-idx +! '\n' character-type exit then
448 S" space" str-equiv? if 5 parse-idx +! bl character-type exit then
449 S" tab" str-equiv? if 3 parse-idx +! 9 character-type exit then
451 nextchar character-type
456 : readstring ( -- charlist )
457 nextchar [char] " = if
462 ." No delimiter following right double quote. Aborting." cr
471 nextchar [char] \ = if
474 [char] n of '\n' endof
475 [char] " of [char] " endof
481 inc-parse-idx character-type
488 : readsymbol ( -- charlist )
489 delim? if nil exit then
491 nextchar inc-parse-idx character-type
498 : charlist-equiv ( charlist charlist -- bool )
507 2drop 2drop true exit
509 2drop 2drop false exit
514 2drop 2drop false exit
521 car drop -rot car drop = if
522 cdr 2swap cdr recurse
528 : charlist>symbol ( charlist -- symbol-obj )
530 symbol-table fetchobj
547 drop symbol-type 2dup
548 symbol-table fetchobj cons
554 : readpair ( -- pairobj )
558 nextchar [char] ) = if
563 ." No delimiter following right paren. Aborting." cr
572 \ Read first pair element
577 nextchar [char] . = if
582 ." No delimiter following '.'. Aborting." cr
596 \ Parse a scheme expression
622 nextchar [char] " <> if
623 bold red ." Missing closing double-quote." reset-term cr
641 nextchar [char] ) <> if
642 bold red ." Missing closing paren." reset-term cr
651 nextchar [char] ' = if
653 quote-symbol recurse nil cons cons exit
657 bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
661 \ Anything else is parsed as a symbol
662 readsymbol charlist>symbol
670 : self-evaluating? ( obj -- obj bool )
671 boolean-type istype? if true exit then
672 number-type istype? if true exit then
673 character-type istype? if true exit then
674 string-type istype? if true exit then
675 nil-type istype? if true exit then
680 : tagged-list? ( obj tag-obj -- obj bool )
682 pair-type istype? false = if
688 : quote? ( obj -- obj bool )
689 quote-symbol tagged-list? ;
691 : quote-body ( quote-obj -- quote-body-obj )
694 : variable? ( obj -- obj bool )
695 symbol-type istype? ;
697 : definition? ( obj -- obj bool )
698 define-symbol tagged-list? ;
700 : definition-var ( obj -- var )
703 : definition-val ( obj -- val )
706 : assignment? ( obj -- obj bool )
707 set!-symbol tagged-list? ;
709 : assignment-var ( obj -- var )
712 : assignment-val ( obj -- val )
717 : eval-definition ( obj env -- res )
719 2over 2over ( env obj env obj )
720 definition-val 2swap ( env obj valexp env )
723 2swap definition-var 2swap ( env var val )
725 >R >R 2swap R> R> 2swap ( var val env )
731 : eval-assignment ( obj env -- res )
733 2over 2over ( env obj env obj )
734 assignment-val 2swap ( env obj valexp env )
737 2swap assignment-var 2swap ( env var val )
739 >R >R 2swap R> R> 2swap ( var val env )
745 :noname ( obj env -- result )
765 2swap eval-definition
770 2swap eval-assignment
774 bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
780 \ ---- Print ---- {{{
782 : printnum ( numobj -- ) drop 0 .R ;
784 : printbool ( numobj -- )
792 : printchar ( charobj -- )
796 bl of ." #\space" endof
797 '\n' of ." #\newline" endof
803 : (printstring) ( stringobj -- )
804 nil-type istype? if 2drop exit then
808 '\n' of ." \n" drop endof
809 [char] \ of ." \\" drop endof
810 [char] " of [char] \ emit [char] " emit drop endof
816 : printstring ( stringobj -- )
821 : printsymbol ( symbolobj -- )
822 nil-type istype? if 2drop exit then
828 : printnil ( nilobj -- )
832 : printpair ( pairobj -- )
836 nil-type istype? if 2drop exit then
837 pair-type istype? if space recurse exit then
842 number-type istype? if printnum exit then
843 boolean-type istype? if printbool exit then
844 character-type istype? if printchar exit then
845 string-type istype? if printstring exit then
846 symbol-type istype? if printsymbol exit then
847 nil-type istype? if printnil exit then
848 pair-type istype? if ." (" printpair ." )" exit then
850 bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
859 cr ." Welcome to scheme.forth.jl!" cr
860 ." Use Ctrl-D to exit." cr
865 cr bold fg green ." > " reset-term
867 global-env fetchobj eval
868 fg cyan ." ; " print reset-term