include term-colours.4th
0 constant number-type
+1 constant boolean-type
+2 constant character-type
: istype? ( obj -- obj b )
over = ;
\ ---- Read ----
variable parse-idx
-variable dummy-parse-idx
+variable stored-parse-idx
+create parse-str 161 allot
+variable parse-str-span
+
+: append-newline
+ 1 parse-str-span +!
+ '\n' parse-str parse-str-span @ + ! ;
+
+: getline
+ parse-str 160 expect
+ span @ parse-str-span !
+ append-newline
+ 0 parse-idx ! ;
+
+: inc-parse-idx
+ 1 parse-idx +! ;
+
+: dec-parse-idx
+ 1 parse-idx -! ;
: store-parse-idx
- parse-idx @ dummy-parse-idx ! ;
+ parse-idx @ stored-parse-idx ! ;
: restore-parse-idx
- dummy-parse-idx @ parse-idx ! ;
+ stored-parse-idx @ parse-idx ! ;
-variable parse-str
: charavailable? ( -- bool )
- parse-str @ @ parse-idx @ >
+ 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 )
nextchar BL =
begin
whitespace?
while
- 1 parse-idx +!
+ inc-parse-idx
repeat
;
then
store-parse-idx
- 1 parse-idx +!
+ inc-parse-idx
begin digit? while
- 1 parse-idx +!
+ inc-parse-idx
repeat
delim? charavailable? false = or if
then
;
+: boolean? ( -- bool )
+ nextchar [char] # <> if false exit then
+
+ store-parse-idx
+ inc-parse-idx
+
+ nextchar [char] t <>
+ nextchar [char] f <>
+ and if restore-parse-idx false exit then
+
+ restore-parse-idx
+ true
+;
+
+: character? ( -- bool )
+ nextchar [char] # <> if false exit then
+
+ store-parse-idx
+ inc-parse-idx
+
+ nextchar [char] \ <> if restore-parse-idx false exit then
+
+ inc-parse-idx
+
+ charavailable? false = if restore-parse-idx false exit then
+
+ restore-parse-idx true
+;
+
: readnum ( -- num-atom )
minus? dup if
- 1 parse-idx +!
+ inc-parse-idx
then
0
begin digit? while
10 * nextchar [char] 0 - +
- 1 parse-idx +!
+ inc-parse-idx
repeat
swap if negate then
number-type
;
-\ Parse a counted string into a scheme expression
+: readbool ( -- bool-atom )
+ inc-parse-idx
+
+ nextchar [char] f = if
+ false
+ else
+ true
+ then
+
+ boolean-type
+;
+
+\ Parse a scheme expression
: read ( -- obj )
eatspaces
+
number? if
readnum
exit
then
- ." Error parsing string at character" parse-idx ? ." . Aborting." cr
+ boolean? if
+ readbool
+ exit
+ then
+
+ bold fg red ." Error parsing string starting at character '"
+ nextchar emit
+ ." '. Aborting." reset-term cr
abort
;
\ ---- Eval ----
: self-evaluating? ( obj -- obj bool )
- number-type istype? ;
+ number-type istype? if true exit then
+ boolean-type istype? if true exit then
+ false ;
: eval
self-evaluating? if
exit
then
- ." Error evaluating expression - unrecognized type. Aborting." cr
+ bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
abort
;
\ ---- Print ----
-: print ( obj -- )
- number-type istype? if
- drop .
+: printnum ( numobj -- ) drop . ;
+
+: printbool ( numobj -- )
+ drop if
+ ." #t"
+ else
+ ." #f"
then
;
-\ ---- REPL ----
-
-create repl-buffer 161 allot
-repl-buffer parse-str !
-
-: getline
- repl-buffer 1+ 160 expect cr span @ repl-buffer ! ;
+: print ( obj -- )
+ ." ; "
+ number-type istype? if ." => " printnum exit then
+ boolean-type istype? if ." => " printbool exit then
+;
-: eof?
- repl-buffer @ 0= if false exit then
- repl-buffer 1+ @ 4 <> if false exit then
- true ;
+\ ---- REPL ----
: repl
cr ." Welcome to scheme.forth.jl!" cr
." Use Ctrl-D to exit." cr
begin
- cr bold fg green ." => " reset-term
- getline
-
- eof? if
- fg blue ." Moriturus te saluto." reset-term
- exit
- then
-
- repl-buffer @ 0> if
- 0 parse-idx !
- read
- eval
- print
- then
+ cr bold fg green ." > " reset-term
+ read
+ eval
+ fg cyan print reset-term
again
;