-\ Scheme interpreter
-
vocabulary scheme
scheme definitions
include term-colours.4th
+include defer-is.4th
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 -- obj b )
over = ;
+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 !
+
+: cons ( car-obj cdr-obj -- pair-obj )
+ cdr-type-cells nextfree @ + !
+ cdr-cells nextfree @ + !
+ car-type-cells nextfree @ + !
+ car-cells nextfree @ + !
+
+ nextfree @ pair-type
+
+ 1 nextfree +!
+;
+
+: car ( pair-obj -- car-obj )
+ drop
+ dup car-cells + @ swap
+ car-type-cells + @
+;
+
+: cdr ( pair-obj -- car-obj )
+ drop
+ dup cdr-cells + @ swap
+ cdr-type-cells + @
+;
+
+
\ ---- Read ----
variable 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 +! ;
: dec-parse-idx
1 parse-idx -! ;
-: store-parse-idx
- parse-idx @ stored-parse-idx ! ;
-
-: restore-parse-idx
- stored-parse-idx @ parse-idx ! ;
-
: charavailable? ( -- bool )
parse-str-span @ parse-idx @ > ;
exit
then
- store-parse-idx
+ push-parse-idx
inc-parse-idx
begin digit? while
inc-parse-idx
repeat
- delim? charavailable? false = or if
- restore-parse-idx
+ delim? if
+ pop-parse-idx
true
else
- restore-parse-idx
+ pop-parse-idx
false
then
;
: boolean? ( -- bool )
nextchar [char] # <> if false exit then
- store-parse-idx
+ push-parse-idx
inc-parse-idx
nextchar [char] t <>
nextchar [char] f <>
- and if restore-parse-idx false exit then
+ 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 )
- restore-parse-idx
- true
+ 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
- store-parse-idx
+ push-parse-idx
inc-parse-idx
- nextchar [char] \ <> if restore-parse-idx false exit then
+ nextchar [char] \ <> if pop-parse-idx false exit then
inc-parse-idx
- charavailable? false = if restore-parse-idx false exit then
+ 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
- restore-parse-idx true
+ pop-parse-idx true
;
+: pair? ( -- bool )
+ nextchar [char] ( = ;
+
+: string? ( -- bool )
+ nextchar [char] " = ;
+
: readnum ( -- num-atom )
minus? dup if
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 ( -- str-obj )
+ 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
+;
+
+defer read
+
+: readpair ( -- obj )
+ 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
+
+ eatspaces read
+ else
+ recurse
+ then
+
+ eatspaces
+
+ cons
+;
+
\ Parse a scheme expression
-: read ( -- obj )
+:noname ( -- obj )
eatspaces
exit
then
+ 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
+
eof? if
bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
quit
nextchar emit
." '. Aborting." reset-term cr
abort
-;
+
+; 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
+ string-type istype? if true exit then
+ nil-type istype? if true exit then
false ;
: eval
- self-evaluating? if
- exit
- then
+ \ self-evaluating? if
+ \ exit
+ \ then
+ exit
bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
abort
\ ---- Print ----
-: printnum ( numobj -- ) drop . ;
+: printnum ( numobj -- ) drop 0 .R ;
: printbool ( numobj -- )
drop if
then
;
-: print ( obj -- )
- ." ; "
+: 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
+
+ 2dup car drop dup
+ case
+ '\n' of ." \n" drop endof
+ [char] \ of ." \\" drop endof
+ [char] " of [char] \ emit [char] " emit drop endof
+ emit
+ endcase
+
+ cdr recurse
+;
+: printstring ( stringobj -- )
+ [char] " emit
+ (printstring)
+ [char] " emit ;
+
+: 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
+;
+
+: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
+ nil-type istype? if printnil exit then
+ pair-type istype? if ." (" printpair ." )" exit then
+
+ bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
+ abort
+; is print
\ ---- REPL ----
cr bold fg green ." > " reset-term
read
eval
- fg cyan print reset-term
+ fg cyan ." ; " print reset-term
again
;
The Lambda Lab / projects / scheme.forth.jl.git / blobdiff