-\ Scheme interpreter
-
vocabulary scheme
scheme definitions
include term-colours.4th
+include defer-is.4th
+
+\ ------ Types ------
0 constant number-type
1 constant boolean-type
2 constant character-type
-: istype? ( obj -- obj b )
+3 constant string-type
+4 constant nil-type
+5 constant pair-type
+6 constant symbol-type
+: istype? ( obj type -- obj bool )
over = ;
+\ ------ Memory ------
+
+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 + @
+;
+
+: nil 0 nil-type ;
+: nil? nil-type istype? ;
+
+: objvar create 0 , 0 , ;
+
+: 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+ @ ;
+
+objvar symbol-table
+nil symbol-table setobj
+
\ ---- Read ----
variable parse-idx
inc-parse-idx
- S" newline" str-equiv? if true exit then
- S" space" str-equiv? if true exit then
- S" tab" str-equiv? if true 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
pop-parse-idx true
;
+: pair? ( -- bool )
+ nextchar [char] ( = ;
+
+: string? ( -- bool )
+ nextchar [char] " = ;
+
+: initial? ( -- bool )
+ nextchar [char] A >= nextchar [char] Z <= and if true exit then
+ nextchar [char] a >= nextchar [char] z <= and if true exit then
+ nextchar [char] * = if true exit then
+ nextchar [char] / = if true exit then
+ nextchar [char] > = if true exit then
+ nextchar [char] < = if true exit then
+ nextchar [char] = = if true exit then
+ nextchar [char] ? = if true exit then
+ nextchar [char] ! = if true exit then
+ false
+;
+
+: symbol? ( -- bool )
+ initial? if true exit then
+ nextchar [char] + =
+ nextchar [char] - = or if
+ inc-parse-idx
+ delim? if dec-parse-idx true exit then
+ dec-parse-idx
+ then
+ false
+;
+
: readnum ( -- num-atom )
minus? dup if
inc-parse-idx
inc-parse-idx
inc-parse-idx
- S" newline" str-equiv? if '\n' character-type exit then
- S" space" str-equiv? if bl character-type exit then
- S" tab" str-equiv? if 9 character-type exit then
+ 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
+ true exit
+ else
+ false exit
+ then
+ else
+ nil? -rot 2drop
+ if
+ 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
+
+ eatspaces read
+ else
+ recurse
+ then
+
+ eatspaces
+
+ cons
+;
+
\ Parse a scheme expression
-: read ( -- obj )
+:noname ( -- obj )
eatspaces
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
+
+ symbol? if
+ readsymbol charlist>symbol
+ 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
- false ;
+ true \ everything self-evaluating for now
+;
: eval
self-evaluating? if
\ ---- Print ----
-: printnum ( numobj -- ) drop . ;
+: printnum ( numobj -- ) drop 0 .R ;
: printbool ( numobj -- )
drop if
bl of ." #\space" endof
'\n' of ." #\newline" endof
- ." #\" emit
+ 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
- trace
+ cdr recurse
;
+: printstring ( stringobj -- )
+ [char] " emit
+ (printstring)
+ [char] " emit ;
+
+: printsymbol ( symbolobj -- )
+ nil-type istype? if 2drop exit then
-: print ( obj -- )
- ." ; "
+ 2dup car drop emit
+ cdr recurse
+;
+
+: 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
+ symbol-type istype? if printsymbol 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