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 ---- {{{
129 : enclosing-env ( env -- env )
132 : first-frame ( env -- frame )
135 : make-frame ( vars vals -- frame )
138 : frame-vars ( frame -- vars )
141 : frame-vals ( frame -- vals )
144 : add-binding ( var val frame -- )
145 2swap 2over frame-vals cons
147 2swap 2over frame-vars cons
151 : extend-env ( vars vals env -- env )
161 : get-vars-vals-frame ( var frame -- bool )
162 2dup frame-vars vars setobj
163 frame-vals vals setobj
166 vars fetchobj nil objeq? false =
168 2dup vars fetchobj car objeq? if
173 vars fetchobj cdr vars setobj
174 vals fetchobj cdr vals setobj
180 : get-vars-vals ( var env -- vars? vals? bool )
183 2dup nil objeq? false =
185 2over 2over first-frame
186 get-vars-vals-frame if
188 vars fetchobj vals fetchobj true
202 : lookup-var ( var env -- val )
206 bold fg red ." Tried to read unbound variable." reset-term cr abort
210 : set-var ( var val env -- )
211 >R >R 2swap R> R> ( val var env )
213 2swap 2drop ( val vals )
216 bold fg red ." Tried to set unbound variable." reset-term cr abort
222 : define-var ( var val env -- )
225 2over env fetchobj ( var val var env )
227 2swap 2drop ( var val vals )
232 first-frame ( var val frame )
240 nil nil nil extend-env
248 variable stored-parse-idx
249 create parse-str 161 allot
250 variable parse-str-span
252 create parse-idx-stack 10 allot
253 variable parse-idx-sp
254 parse-idx-stack parse-idx-sp !
257 parse-idx @ parse-idx-sp @ !
262 parse-idx-sp @ parse-idx-stack <= abort" Parse index stack underflow."
266 parse-idx-sp @ @ parse-idx ! ;
270 '\n' parse-str parse-str-span @ + !
271 1 parse-str-span +! ;
278 parse-str 160 expect cr
279 span @ parse-str-span !
289 : charavailable? ( -- bool )
290 parse-str-span @ parse-idx @ > ;
292 : nextchar ( -- char )
293 charavailable? false = if getline then
294 parse-str parse-idx @ + @ ;
296 : whitespace? ( -- bool )
305 nextchar [char] ( = or
306 nextchar [char] ) = or
323 nextchar [char] - = ;
325 : number? ( -- bool )
326 digit? minus? or false = if
347 : boolean? ( -- bool )
348 nextchar [char] # <> if false exit then
355 and if pop-parse-idx false exit then
367 : str-equiv? ( str -- bool )
384 delim? false = if drop false then
389 : character? ( -- bool )
390 nextchar [char] # <> if false exit then
395 nextchar [char] \ <> if pop-parse-idx false exit then
399 S" newline" str-equiv? if pop-parse-idx true exit then
400 S" space" str-equiv? if pop-parse-idx true exit then
401 S" tab" str-equiv? if pop-parse-idx true exit then
403 charavailable? false = if pop-parse-idx false exit then
409 nextchar [char] ( = ;
411 : string? ( -- bool )
412 nextchar [char] " = ;
414 : readnum ( -- num-atom )
422 10 * nextchar [char] 0 - +
431 : readbool ( -- bool-atom )
434 nextchar [char] f = if
445 : readchar ( -- char-atom )
449 S" newline" str-equiv? if 7 parse-idx +! '\n' character-type exit then
450 S" space" str-equiv? if 5 parse-idx +! bl character-type exit then
451 S" tab" str-equiv? if 3 parse-idx +! 9 character-type exit then
453 nextchar character-type
458 : readstring ( -- charlist )
459 nextchar [char] " = if
464 ." No delimiter following right double quote. Aborting." cr
473 nextchar [char] \ = if
476 [char] n of '\n' endof
477 [char] " of [char] " endof
483 inc-parse-idx character-type
490 : readsymbol ( -- charlist )
491 delim? if nil exit then
493 nextchar inc-parse-idx character-type
500 : charlist-equiv ( charlist charlist -- bool )
509 2drop 2drop true exit
511 2drop 2drop false exit
516 2drop 2drop false exit
523 car drop -rot car drop = if
524 cdr 2swap cdr recurse
530 : charlist>symbol ( charlist -- symbol-obj )
532 symbol-table fetchobj
549 drop symbol-type 2dup
550 symbol-table fetchobj cons
556 : readpair ( -- pairobj )
560 nextchar [char] ) = if
565 ." No delimiter following right paren. Aborting." cr
574 \ Read first pair element
579 nextchar [char] . = if
584 ." No delimiter following '.'. Aborting." cr
598 \ Parse a scheme expression
624 nextchar [char] " <> if
625 bold red ." Missing closing double-quote." reset-term cr
643 nextchar [char] ) <> if
644 bold red ." Missing closing paren." reset-term cr
653 nextchar [char] ' = if
655 quote-symbol recurse nil cons cons exit
659 bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
663 \ Anything else is parsed as a symbol
664 readsymbol charlist>symbol
672 : self-evaluating? ( obj -- obj bool )
673 boolean-type istype? if true exit then
674 number-type istype? if true exit then
675 character-type istype? if true exit then
676 string-type istype? if true exit then
677 nil-type istype? if true exit then
682 : tagged-list? ( obj tag-obj -- obj bool )
684 pair-type istype? false = if
690 : quote? ( obj -- obj bool )
691 quote-symbol tagged-list? ;
693 : quote-body ( quote-obj -- quote-body-obj )
696 : variable? ( obj -- obj bool )
697 symbol-type istype? ;
699 : definition? ( obj -- obj bool )
700 define-symbol tagged-list? ;
702 : definition-var ( obj -- var )
705 : definition-val ( obj -- val )
708 : assignment? ( obj -- obj bool )
709 set!-symbol tagged-list? ;
711 : assignment-var ( obj -- var )
714 : assignment-val ( obj -- val )
719 : eval-definition ( obj env -- res )
721 2over 2over ( env obj env obj )
722 definition-val 2swap ( env obj valexp env )
725 2swap definition-var 2swap ( env var val )
727 >R >R 2swap R> R> 2swap ( var val env )
733 : eval-assignment ( obj env -- res )
735 2over 2over ( env obj env obj )
736 assignment-val 2swap ( env obj valexp env )
739 2swap assignment-var 2swap ( env var val )
741 >R >R 2swap R> R> 2swap ( var val env )
747 :noname ( obj env -- result )
767 2swap eval-definition
772 2swap eval-assignment
776 bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
782 \ ---- Print ---- {{{
784 : printnum ( numobj -- ) drop 0 .R ;
786 : printbool ( numobj -- )
794 : printchar ( charobj -- )
798 bl of ." #\space" endof
799 '\n' of ." #\newline" endof
805 : (printstring) ( stringobj -- )
806 nil-type istype? if 2drop exit then
810 '\n' of ." \n" drop endof
811 [char] \ of ." \\" drop endof
812 [char] " of [char] \ emit [char] " emit drop endof
818 : printstring ( stringobj -- )
823 : printsymbol ( symbolobj -- )
824 nil-type istype? if 2drop exit then
830 : printnil ( nilobj -- )
834 : printpair ( pairobj -- )
838 nil-type istype? if 2drop exit then
839 pair-type istype? if space recurse exit then
844 number-type istype? if printnum exit then
845 boolean-type istype? if printbool exit then
846 character-type istype? if printchar exit then
847 string-type istype? if printstring exit then
848 symbol-type istype? if printsymbol exit then
849 nil-type istype? if printnil exit then
850 pair-type istype? if ." (" printpair ." )" exit then
852 bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
861 cr ." Welcome to scheme.forth.jl!" cr
862 ." Use Ctrl-D to exit." cr
867 cr bold fg green ." > " reset-term
869 global-env fetchobj eval
870 fg cyan ." ; " print reset-term