-\ Scheme interpreter
-
vocabulary scheme
scheme definitions
-\ Cons cell memory
-1000 constant memsize
-create car memsize allot
-create cdr memsize allot
-create types memsize allot
+include term-colours.4th
+include defer-is.4th
+
+\ ------ Types ------
+
+0 constant number-type
+1 constant boolean-type
+2 constant character-type
+3 constant string-type
+4 constant nil-type
+5 constant pair-type
+6 constant symbol-type
+: istype? ( obj type -- obj bool )
+ over = ;
-0 constant symbol-type
-1 constant int-type
-2 constant list-type
-3 constant bool-type
+\ ------ Cons cell memory ------ {{{
+
+1000 constant N
+create car-cells N allot
+create car-type-cells N allot
+create cdr-cells N allot
+create cdr-type-cells N allot
variable nextfree
0 nextfree !
-: stack
- create here 1+ , allot ;
+: cons ( car-obj cdr-obj -- pair-obj )
+ cdr-type-cells nextfree @ + !
+ cdr-cells nextfree @ + !
+ car-type-cells nextfree @ + !
+ car-cells nextfree @ + !
+ nextfree @ pair-type
-: push ( st v -- )
- over @ !
- 1 swap +!
+ 1 nextfree +!
;
-: pop ( st -- v )
- dup @ ( s0 sp )
- 1- ( so sp' )
+: car ( pair-obj -- car-obj )
+ drop
+ dup car-cells + @ swap
+ car-type-cells + @
+;
- 2dup = abort" Stack underflow."
-
- dup @ ( s0 sp' v )
- -rot swap ( v sp' s0 )
- !
+: cdr ( pair-obj -- car-obj )
+ drop
+ dup cdr-cells + @ swap
+ cdr-type-cells + @
;
-100 stack parse-stack
-variable parse-idx
-variable parse-str
+: set-car! ( obj pair-obj -- )
+ drop dup
+ rot swap car-type-cells + !
+ car-cells + !
+;
+
+: set-cdr! ( obj pair-obj -- )
+ drop dup
+ rot swap cdr-type-cells + !
+ cdr-cells + !
+;
+
+: caar car car ;
+: cadr cdr car ;
+: cdar car cdr ;
+: cddr cdr cdr ;
+
+: nil 0 nil-type ;
+: nil? nil-type istype? ;
+
+: objvar create nil swap , , ;
+
+: value@ ( objvar -- val ) @ ;
+: type@ ( objvar -- type ) 1+ @ ;
+: value! ( newval objvar -- ) ! ;
+: type! ( newtype objvar -- ) 1+ ! ;
+: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ;
+: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ;
+
+: objeq? ( obj obj -- bool )
+ rot = -rot = and ;
+
+\ }}}
+
+\ ---- Pre-defined symbols ---- {{{
+objvar symbol-table
-: inc-parse-idx parse-idx +! ;
-: dec-parse-idx parse-idx -! ;
+: (create-symbol) ( addr n -- symbol-obj )
+ dup 0= if
+ 2drop nil
+ else
+ 2dup drop @ character-type 2swap
+ swap 1+ swap 1-
+ recurse
-: ?charavailable ( -- bool )
- parse-str @ @ parse-idx @ >
+ cons
+ then
;
-: nextchar ( -- char )
- ?charavailable if
- parse-str @ 1+ parse-idx @ + @
+: create-symbol ( -- )
+ bl word
+ count
+
+ (create-symbol)
+ drop symbol-type
+
+ 2dup
+
+ symbol-table fetchobj
+ cons
+ symbol-table setobj
+
+ create swap , ,
+ does> dup @ swap 1+ @
+;
+
+create-symbol quote quote-symbol
+create-symbol define define-symbol
+create-symbol set! set!-symbol
+create-symbol ok ok-symbol
+
+\ }}}
+
+\ ---- Environments ---- {{{
+
+objvar global-env
+
+: enclosing-env ( env -- env )
+ cdr ;
+
+: first-frame ( env -- frame )
+ car ;
+
+: make-frame ( vars vals -- frame )
+ cons ;
+
+: frame-vars ( frame -- vars )
+ car ;
+
+: frame-vals ( frame -- vals )
+ cdr ;
+
+: add-binding ( var val frame -- )
+ 2swap 2over frame-vals cons
+ 2over set-car!
+ 2swap 2over frame-vars cons
+ swap set-cdr!
+;
+
+: extend-env ( vars vals env -- env )
+ >R >R
+ make-frame
+ R> R>
+ cons
+;
+
+objvar vars
+objvar vals
+
+: get-vars-vals-frame ( var frame -- bool )
+ 2dup frame-vars vars setobj
+ frame-vals vals setobj
+
+ begin
+ vars fetchobj nil objeq? false =
+ while
+ 2dup vars fetchobj car objeq? if
+ 2drop true
+ exit
+ then
+
+ vars fetchobj cdr vars setobj
+ vals fetchobj cdr vals setobj
+ repeat
+
+ 2drop false
+;
+
+: get-vars-vals ( var env -- vars? vals? bool )
+
+ begin
+ 2dup nil objeq? false =
+ while
+ 2over 2over first-frame
+ lookup-var-frame if
+ 2drop 2drop
+ vars fetchobj vals fetchobj true
+ exit
+ then
+
+ enclosing-env
+ repeat
+
+ 2drop 2drop
+ false
+;
+
+hide vars
+hide vals
+
+: lookup-var ( var env -- val )
+ get-vars-vals if
+ 2swap 2drop car
else
- 0
+ bold fg red ." Tried to read unbound variable." reset-term abort
then
;
-: ?whitespace ( -- bool )
- nextchar BL =
- nextchar '\n' = or
+: set-var ( var val env -- )
+ >R >R 2swap R> R> ( val var env )
+ get-vars-vals if
+ 2swap 2drop ( val vals )
+ set-car!
+ else
+ bold fg red ." Tried to set unbound variable." reset-term abort
+ then
;
-: ?delim ( -- bool )
- ?whitespace
+objvar env
+
+: define-var ( var val env -- )
+ env objset
+
+ 2over env objfetch ( var val var env )
+ get-vars-vals if
+ 2swap 2drop ( var val vals )
+ set-car!
+ 2drop
+ else
+ env objfetch
+ first-frame ( var val frame )
+ add-binding
+ then
+;
+
+hide env
+
+\ }}}
+
+\ ---- Read ---- {{{
+
+variable parse-idx
+variable stored-parse-idx
+create parse-str 161 allot
+variable parse-str-span
+
+create parse-idx-stack 10 allot
+variable parse-idx-sp
+parse-idx-stack parse-idx-sp !
+
+: push-parse-idx
+ parse-idx @ parse-idx-sp @ !
+ 1 parse-idx-sp +!
+;
+
+: pop-parse-idx
+ parse-idx-sp @ parse-idx-stack <= abort" Parse index stack underflow."
+
+ 1 parse-idx-sp -!
+
+ parse-idx-sp @ @ parse-idx ! ;
+
+
+: append-newline
+ '\n' parse-str parse-str-span @ + !
+ 1 parse-str-span +! ;
+
+: empty-parse-str
+ 0 parse-str-span !
+ 0 parse-idx ! ;
+
+: getline
+ parse-str 160 expect cr
+ span @ parse-str-span !
+ append-newline
+ 0 parse-idx ! ;
+
+: inc-parse-idx
+ 1 parse-idx +! ;
+
+: dec-parse-idx
+ 1 parse-idx -! ;
+
+: charavailable? ( -- bool )
+ parse-str-span @ parse-idx @ > ;
+
+: nextchar ( -- char )
+ charavailable? false = if getline then
+ parse-str parse-idx @ + @ ;
+
+: whitespace? ( -- bool )
+ nextchar BL =
+ nextchar '\n' = or ;
+
+: eof? ( -- bool )
+ nextchar 4 = ;
+
+: delim? ( -- bool )
+ whitespace?
nextchar [char] ( = or
nextchar [char] ) = or
;
: eatspaces
begin
- ?whitespace
+ whitespace?
while
- 1 parse-idx +!
+ inc-parse-idx
repeat
;
-: parsebool
+: digit? ( -- bool )
+ nextchar [char] 0 >=
+ nextchar [char] 9 <=
+ and ;
- nextchar emit cr
- trace
+: minus? ( -- bool )
+ nextchar [char] - = ;
- false
- nextchar [char] # <> if exit then
+: number? ( -- bool )
+ digit? minus? or false = if
+ false
+ exit
+ then
+
+ push-parse-idx
+ inc-parse-idx
+
+ begin digit? while
+ inc-parse-idx
+ repeat
+
+ delim? if
+ pop-parse-idx
+ true
+ else
+ pop-parse-idx
+ false
+ then
+;
+
+: boolean? ( -- bool )
+ nextchar [char] # <> if false exit then
+
+ push-parse-idx
+ inc-parse-idx
+
+ nextchar [char] t <>
+ nextchar [char] f <>
+ and if pop-parse-idx false exit then
+
+ inc-parse-idx
+ delim? if
+ pop-parse-idx
+ true
+ else
+ pop-parse-idx
+ false
+ then
+;
+
+: str-equiv? ( str -- bool )
+
+ push-parse-idx
+
+ true -rot
+
+ swap dup rot + swap
+
+ do
+ i @ nextchar <> if
+ drop false
+ leave
+ then
+
+ inc-parse-idx
+ loop
+
+ delim? false = if drop false then
+
+ pop-parse-idx
+;
+
+: character? ( -- bool )
+ nextchar [char] # <> if false exit then
+
+ push-parse-idx
+ inc-parse-idx
+
+ nextchar [char] \ <> if pop-parse-idx false exit then
+
+ inc-parse-idx
+
+ S" newline" str-equiv? if pop-parse-idx true exit then
+ S" space" str-equiv? if pop-parse-idx true exit then
+ S" tab" str-equiv? if pop-parse-idx true exit then
+
+ charavailable? false = if pop-parse-idx false exit then
+
+ pop-parse-idx true
+;
+
+: pair? ( -- bool )
+ nextchar [char] ( = ;
+
+: string? ( -- bool )
+ nextchar [char] " = ;
+
+: readnum ( -- num-atom )
+ minus? dup if
+ inc-parse-idx
+ then
+
+ 0
+
+ begin digit? while
+ 10 * nextchar [char] 0 - +
+ inc-parse-idx
+ repeat
+
+ swap if negate then
+
+ number-type
+;
+
+: readbool ( -- bool-atom )
+ inc-parse-idx
+
+ nextchar [char] f = if
+ false
+ else
+ true
+ then
+
+ inc-parse-idx
+
+ boolean-type
+;
+
+: readchar ( -- char-atom )
+ inc-parse-idx
+ inc-parse-idx
+
+ S" newline" str-equiv? if 7 parse-idx +! '\n' character-type exit then
+ S" space" str-equiv? if 5 parse-idx +! bl character-type exit then
+ S" tab" str-equiv? if 3 parse-idx +! 9 character-type exit then
+
+ nextchar character-type
+
+ inc-parse-idx
+;
+
+: readstring ( -- charlist )
+ nextchar [char] " = if
+ inc-parse-idx
+
+ delim? false = if
+ bold fg red
+ ." No delimiter following right double quote. Aborting." cr
+ reset-term abort
+ then
+
+ dec-parse-idx
+
+ 0 nil-type exit
+ then
+
+ nextchar [char] \ = if
+ inc-parse-idx
+ nextchar case
+ [char] n of '\n' endof
+ [char] " of [char] " endof
+ [char] \
+ endcase
+ else
+ nextchar
+ then
+ inc-parse-idx character-type
+
+ recurse
+
+ cons
+;
+
+: readsymbol ( -- charlist )
+ delim? if nil exit then
+
+ nextchar inc-parse-idx character-type
+
+ recurse
+
+ cons
+;
+
+: charlist-equiv ( charlist charlist -- bool )
+
+ 2over 2over
+
+ \ One or both nil
+ nil? -rot 2drop
+ if
+ nil? -rot 2drop
+ if
+ 2drop 2drop true exit
+ else
+ 2drop 2drop false exit
+ then
+ else
+ nil? -rot 2drop
+ if
+ 2drop 2drop false exit
+ then
+ then
+
+ 2over 2over
+
+ \ Neither nil
+ car drop -rot car drop = if
+ cdr 2swap cdr recurse
+ else
+ 2drop 2drop false
+ then
+;
+
+: charlist>symbol ( charlist -- symbol-obj )
+
+ symbol-table fetchobj
+
+ begin
+ nil? false =
+ while
+ 2over 2over
+ car drop pair-type
+ charlist-equiv if
+ 2swap 2drop
+ car
+ exit
+ else
+ cdr
+ then
+ repeat
+
+ 2drop
+ drop symbol-type 2dup
+ symbol-table fetchobj cons
+ symbol-table setobj
+;
+
+defer read
+
+: readpair ( -- pairobj )
+ eatspaces
+
+ \ Empty lists
+ nextchar [char] ) = if
+ inc-parse-idx
+
+ delim? false = if
+ bold fg red
+ ." No delimiter following right paren. Aborting." cr
+ reset-term abort
+ then
+
+ dec-parse-idx
+
+ 0 nil-type exit
+ then
+
+ \ Read first pair element
+ read
+
+ \ Pairs
+ eatspaces
+ nextchar [char] . = if
+ inc-parse-idx
+
+ delim? false = if
+ bold fg red
+ ." No delimiter following '.'. Aborting." cr
+ reset-term abort
+ then
- 1 inc-parse-idx
+ eatspaces read
+ else
+ recurse
+ then
+
+ eatspaces
- nextchar dup [char] t = swap [char] f = or
- not if
- 1 dec-parse-idx
+ cons
+;
+
+\ Parse a scheme expression
+:noname ( -- obj )
+
+ eatspaces
+
+ number? if
+ readnum
exit
then
- 1 inc-parse-idx
+ boolean? if
+ readbool
+ exit
+ then
- ?delim not if
- 2 dec-parse-idx
+ character? if
+ readchar
exit
then
+
+ string? if
+ inc-parse-idx
+
+ readstring
+ drop string-type
+
+ nextchar [char] " <> if
+ bold red ." Missing closing double-quote." reset-term cr
+ abort
+ then
+
+ inc-parse-idx
+
+ exit
+ then
+
+ pair? if
+ inc-parse-idx
+
+ eatspaces
+
+ readpair
+
+ eatspaces
+
+ nextchar [char] ) <> if
+ bold red ." Missing closing paren." reset-term cr
+ abort
+ then
+
+ inc-parse-idx
+
+ exit
+ then
+
+ nextchar [char] ' = if
+ inc-parse-idx
+ quote-symbol recurse nil cons cons exit
+ then
+
+ eof? if
+ bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
+ quit
+ then
+
+ \ Anything else is parsed as a symbol
+ readsymbol charlist>symbol
+
+; is read
+
+\ }}}
+
+\ ---- Eval ---- {{{
+
+: self-evaluating? ( obj -- obj bool )
+ boolean-type istype? if true exit then
+ number-type istype? if true exit then
+ character-type istype? if true exit then
+ string-type istype? if true exit then
+ nil-type istype? if true exit then
+
+ false
;
-: parsetoken
+: tagged-list? ( obj tag-obj -- obj bool )
+ 2over
+ pair-type istype? false = if
+ 2drop 2drop false
+ else
+ car objeq?
+ then ;
- eatspaces
+: quote? ( obj -- obj bool )
+ quote-symbol tagged-list? ;
+
+: quote-body ( quote-obj -- quote-body-obj )
+ cadr ;
+
+: variable? ( obj -- obj bool )
+ symbol-type istype? ;
- \ Parens
+: definition? ( obj -- obj bool )
+ define-symbol tagged-list? ;
- nextchar [char] ( = if
- \ todo
+: definition-var ( obj -- var )
+ cdr car ;
+
+: definition-val ( obj -- val )
+ cdr cdr car ;
+
+: assignment? ( obj -- obj bool )
+ set-symbol tagged-list? ;
+
+: assignment-var ( obj -- var )
+ cdr car ;
+
+: assignment-val ( obj -- val )
+ cdr cdr car ;
+
+: eval-definition ( obj env -- res )
+ 2swap
+ 2over 2over ( env obj env obj )
+ definition-val 2swap ( env obj valexp env )
+ eval ( env obj val )
+
+ 2swap definition-var 2swap ( env var val )
+
+ >R >R 2swap R> R> 2swap ( var val env )
+ define-var
+
+ ok-symbol
+;
+
+: eval-assignment ( obj env -- res )
+ 2swap
+ 2over 2over ( env obj env obj )
+ assignment-val 2swap ( env obj valexp env )
+ eval ( env obj val )
+
+ 2swap assignment-var 2swap ( env var val )
+
+ >R >R 2swap R> R> 2swap ( var val env )
+ set-var
+
+ ok-symbol
+;
+: eval ( obj env -- result )
+ 2swap
+
+ self-evaluating? if
+ 2swap 2drop
exit
then
- nextchar [char] ) = if
- \ todo
+ quote? if
+ quote-body
+ 2swap 2drop
+ exit
+ then
+
+ variable? if
+ 2swap lookup-var
+ exit
+ then
+
+ definition? if
+ 2swap eval-definition
exit
then
- parsebool if
+ assignment? if
+ 2swap eval-assignment
exit
- exit
+ then
+
+ bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
+ abort
;
-\ Parse a counted string into a scheme expression
-: parseexp ( straddr n -- exp )
- 0 parse-idx !
+\ }}}
- begin
- parsetoken
- nextchar 0 =
- until
+\ ---- Print ---- {{{
+
+: printnum ( numobj -- ) drop 0 .R ;
+
+: printbool ( numobj -- )
+ drop if
+ ." #t"
+ else
+ ." #f"
+ then
;
-\ ---- REPL ----
+: printchar ( charobj -- )
+ drop
+ case
+ 9 of ." #\tab" endof
+ bl of ." #\space" endof
+ '\n' of ." #\newline" endof
+
+ dup ." #\" emit
+ endcase
+;
+
+: (printstring) ( stringobj -- )
+ nil-type istype? if 2drop exit then
-: escape 27 emit [char] [ emit ;
-: escape-end [char] m emit ;
+ 2dup car drop dup
+ case
+ '\n' of ." \n" drop endof
+ [char] \ of ." \\" drop endof
+ [char] " of [char] \ emit [char] " emit drop endof
+ emit
+ endcase
-: set-term-colour
- escape [char] 3 emit [char] 0 + emit escape-end
+ cdr recurse
;
+: printstring ( stringobj -- )
+ [char] " emit
+ (printstring)
+ [char] " emit ;
-: reset-term
- escape [char] 0 escape-end
+: printsymbol ( symbolobj -- )
+ nil-type istype? if 2drop exit then
+
+ 2dup car drop emit
+ cdr recurse
;
-: colour
- create ,
-does>
- @ set-term-colour
+: printnil ( nilobj -- )
+ 2drop ." ()" ;
+
+defer print
+: printpair ( pairobj -- )
+ 2dup
+ car print
+ cdr
+ nil-type istype? if 2drop exit then
+ pair-type istype? if space recurse exit then
+ ." . " print
;
-1 colour red
-2 colour green
-3 colour yellow
-4 colour blue
-5 colour magenta
-6 colour cyan
-7 colour white
+:noname ( obj -- )
+ number-type istype? if printnum exit then
+ boolean-type istype? if printbool exit then
+ character-type istype? if printchar exit then
+ string-type istype? if printstring exit then
+ symbol-type istype? if printsymbol exit then
+ nil-type istype? if printnil exit then
+ pair-type istype? if ." (" printpair ." )" exit then
-create repl-buffer 161 allot
+ bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
+ abort
+; is print
-: repl
- repl-buffer parse-str !
+\ }}}
- cr
+\ ---- REPL ----
- begin
- green ." => " white
+: repl
+ cr ." Welcome to scheme.forth.jl!" cr
+ ." Use Ctrl-D to exit." cr
- repl-buffer 1+ 160 expect cr
- span @ repl-buffer !
+ empty-parse-str
- parseexp
- \ eval
+ begin
+ cr bold fg green ." > " reset-term
+ read
+ global-env fetchobj eval
+ fg cyan ." ; " print reset-term
again
;
The Lambda Lab / projects / scheme.forth.jl.git / blobdiff