-\ 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
+
+0 constant number-type
+1 constant boolean-type
+2 constant character-type
+3 constant nil-type
+4 constant pair-type
+: istype? ( obj -- obj b )
+ over = ;
-0 constant symbol-type
-1 constant int-type
-2 constant list-type
-3 constant bool-type
+100 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
+\ ---- Read ----
+
+variable parse-idx
+variable stored-parse-idx
+create parse-str 161 allot
+variable parse-str-span
-: inc-parse-idx parse-idx +! ;
-: dec-parse-idx parse-idx -! ;
+create parse-idx-stack 10 allot
+variable parse-idx-sp
+parse-idx-stack parse-idx-sp !
-: ?charavailable ( -- bool )
- parse-str @ @ parse-idx @ >
+: 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 if
- parse-str @ 1+ parse-idx @ + @
- else
- 0
- then
-;
+ charavailable? false = if getline then
+ parse-str parse-idx @ + @ ;
-: ?whitespace ( -- bool )
+: whitespace? ( -- bool )
nextchar BL =
- nextchar '\n' = or
-;
+ nextchar '\n' = or ;
-: ?delim ( -- bool )
- ?whitespace
+: 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
- 1 inc-parse-idx
+ push-parse-idx
+ inc-parse-idx
- nextchar dup [char] t = swap [char] f = or
- not if
- 1 dec-parse-idx
- exit
+ begin digit? while
+ inc-parse-idx
+ repeat
+
+ delim? if
+ pop-parse-idx
+ true
+ else
+ pop-parse-idx
+ false
then
+;
- 1 inc-parse-idx
+: boolean? ( -- bool )
+ nextchar [char] # <> if false exit then
- ?delim not if
- 2 dec-parse-idx
- exit
+ 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] ( = ;
+
+
+: 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
+;
+
+defer read
+
+: readpair ( -- obj )
+ inc-parse-idx
+ 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
+
+ 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
+
+ eatspaces read
+ else
+ recurse
then
+
+ eatspaces
+
+ cons
;
-: parsetoken
+\ Parse a scheme expression
+:noname ( -- obj )
eatspaces
- \ Parens
+ number? if
+ readnum
+ exit
+ then
- nextchar [char] ( = if
- \ todo
+ boolean? if
+ readbool
exit
then
- nextchar [char] ) = if
- \ todo
+ character? if
+ readchar
exit
then
- parsebool if
+ pair? if
+ readpair
exit
- exit
-;
+ then
+
+ eof? if
+ bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
+ quit
+ then
-\ Parse a counted string into a scheme expression
-: parseexp ( straddr n -- exp )
- 0 parse-idx !
+ bold fg red ." Error parsing string starting at character '"
+ nextchar emit
+ ." '. Aborting." reset-term cr
+ abort
- begin
- parsetoken
- nextchar 0 =
- until
+; is read
+
+\ ---- Eval ----
+
+: self-evaluating? ( obj -- obj bool )
+ number-type istype? if true exit then
+ boolean-type istype? if true exit then
+ character-type istype? if true exit then
+ nil-type istype? if true exit then
+ false ;
+
+: eval
+ \ self-evaluating? if
+ \ exit
+ \ then
+ exit
+
+ bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
+ abort
;
-\ ---- REPL ----
+\ ---- Print ----
-: escape 27 emit [char] [ emit ;
-: escape-end [char] m emit ;
+: printnum ( numobj -- ) drop 0 .R ;
-: set-term-colour
- escape [char] 3 emit [char] 0 + emit escape-end
+: printbool ( numobj -- )
+ drop if
+ ." #t"
+ else
+ ." #f"
+ then
;
-: reset-term
- escape [char] 0 escape-end
+: printchar ( charobj -- )
+ drop
+ case
+ 9 of ." #\tab" endof
+ bl of ." #\space" endof
+ '\n' of ." #\newline" endof
+
+ dup ." #\" emit
+ endcase
;
-: colour
- create ,
-does>
- @ set-term-colour
+: printnil ( nilobj -- )
+ drop ." ()" ;
+
+defer print
+: printpair ( pairobj -- )
+ ." ("
+ 2dup
+ car print
+ cdr
+ nil-type istype? if 2drop ." )" exit then
+ pair-type istype? if 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
+ 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
- repl-buffer parse-str !
+ cr ." Welcome to scheme.forth.jl!" cr
+ ." Use Ctrl-D to exit." cr
- cr
+ empty-parse-str
begin
- green ." => " white
-
- repl-buffer 1+ 160 expect cr
- span @ repl-buffer !
-
- parseexp
- \ eval
+ cr bold fg green ." > " reset-term
+ read
+ eval
+ fg cyan ." ; " print reset-term
again
;
The Lambda Lab / projects / scheme.forth.jl.git / blobdiff