-\ Scheme interpreter
+vocabulary scheme
+scheme definitions
+
+include term-colours.4th
+include defer-is.4th
+include float.4th
+
+include debugging.4th
+
+defer read
+defer eval
+defer print
+
+defer collect-garbage
+
+\ ------ Types ------
+
+variable nexttype
+0 nexttype !
+: make-type
+ create nexttype @ ,
+ 1 nexttype +!
+ does> @ ;
+
+make-type fixnum-type
+make-type realnum-type
+make-type boolean-type
+make-type character-type
+make-type string-type
+make-type nil-type
+make-type none-type
+make-type pair-type
+make-type symbol-type
+make-type primitive-proc-type
+make-type compound-proc-type
+make-type fileport-type
+: istype? ( obj type -- obj bool )
+ over = ;
+
+\ ---- List-structured memory ---- {{{
+
+10000 constant scheme-memsize
+
+create car-cells scheme-memsize allot
+create car-type-cells scheme-memsize allot
+create cdr-cells scheme-memsize allot
+create cdr-type-cells scheme-memsize allot
+
+create nextfrees scheme-memsize allot
+:noname
+ scheme-memsize 0 do
+ i 1+ nextfrees i + !
+ loop
+; execute
+
+variable nextfree
+0 nextfree !
+
+: inc-nextfree
+ nextfrees nextfree @ + @
+ nextfree !
+
+ nextfree @ scheme-memsize >= if
+ collect-garbage
+ then
+
+ nextfree @ scheme-memsize >= if
+ fg red bold
+ ." Out of memory! Aborting."
+ reset-term abort
+ then
+;
+
+: cons ( car-obj cdr-obj -- pair-obj )
+ cdr-type-cells nextfree @ + !
+ cdr-cells nextfree @ + !
+ car-type-cells nextfree @ + !
+ car-cells nextfree @ + !
+
+ nextfree @ pair-type
+ inc-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 + @
+;
+
+: 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? ;
+
+: none 0 none-type ;
+: none? none-type istype? ;
+
+: objvar create nil swap , , ;
+
+: value@ ( objvar -- val ) @ ;
+: type@ ( objvar -- type ) 1+ @ ;
+: value! ( newval objvar -- ) ! ;
+: type! ( newtype objvar -- ) 1+ ! ;
+: obj! ( newobj objvar -- ) dup rot swap 1+ ! ! ;
+: obj@ ( objvar -- obj ) dup @ swap 1+ @ ;
+
+: objeq? ( obj obj -- bool )
+ rot = -rot = and ;
+
+: 2rot ( a1 a2 b1 b2 c1 c2 -- b1 b2 c1 c2 a1 a2 )
+ >R >R ( a1 a2 b1 b2 )
+ 2swap ( b1 b2 a1 a2 )
+ R> R> ( b1 b2 a1 a2 c1 c2 )
+ 2swap
+;
+
+: -2rot ( a1 a2 b1 b2 c1 c2 -- c1 c2 a1 a2 b1 b2 )
+ 2swap ( a1 a2 c1 c2 b1 b2 )
+ >R >R ( a1 a2 c1 c2 )
+ 2swap ( c1 c2 a1 a2 )
+ R> R>
+;
+
+\ }}}
+
+\ ---- Port I/O ---- {{{
+
+: fileport>fid ( fileport -- fid )
+ drop ;
+
+: fid>fileport ( fid -- fileport )
+ fileport-type ;
+
+: open-input-file ( addr n -- fileport )
+ r/o open-file drop fid>fileport
+;
+
+: close-port ( fileport -- )
+ fileport>fid close-file drop
+;
+
+objvar console-i/o-port
+0 fileport-type console-i/o-port obj!
+
+objvar current-input-port
+console-i/o-port obj@ current-input-port obj!
+
+: read-port ( fileport -- obj )
+ current-input-port obj!
+ read ;
+
+: read-console ( -- obj )
+ console-i/o-port obj@ read-port ;
+
+\ }}}
+
+\ ---- Pre-defined symbols ---- {{{
+
+objvar symbol-table
+
+: duplicate-charlist ( charlist -- copy )
+ nil? false = if
+ 2dup car 2swap cdr recurse cons
+ then ;
+
+: 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 obj@
+
+ 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 obj@ cons
+ symbol-table obj!
+;
+
+
+: cstr>charlist ( addr n -- charlist )
+ dup 0= if
+ 2drop nil
+ else
+ 2dup drop @ character-type 2swap
+ swap 1+ swap 1-
+ recurse
+
+ cons
+ then
+;
+
+: create-symbol ( -- )
+ bl word
+ count
+
+ cstr>charlist
+ charlist>symbol
+
+ create swap , ,
+ does> dup @ swap 1+ @
+;
+
+create-symbol quote quote-symbol
+create-symbol define define-symbol
+create-symbol define-macro define-macro-symbol
+create-symbol set! set!-symbol
+create-symbol ok ok-symbol
+create-symbol if if-symbol
+create-symbol lambda lambda-symbol
+create-symbol λ λ-symbol
+create-symbol begin begin-symbol
+
+\ }}}
+
+\ ---- Environments ---- {{{
+
+: 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-cdr!
+ 2swap 2over frame-vars cons
+ 2swap set-car!
+;
+
+: 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 obj!
+ frame-vals vals obj!
+
+ begin
+ vars obj@ nil objeq? false =
+ while
+ 2dup vars obj@ car objeq? if
+ 2drop true
+ exit
+ then
+
+ vars obj@ cdr vars obj!
+ vals obj@ cdr vals obj!
+ repeat
+
+ 2drop false
+;
+
+: get-vars-vals ( var env -- vars? vals? bool )
+
+ begin
+ nil? false =
+ while
+ 2over 2over first-frame
+ get-vars-vals-frame if
+ 2drop 2drop
+ vars obj@ vals obj@ 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
+ bold fg red ." Tried to read unbound variable." reset-term cr abort
+ then
+;
+
+: 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 cr abort
+ then
+;
+
+objvar env
+
+: define-var ( var val env -- )
+ env obj!
+
+ 2over env obj@ ( var val var env )
+ get-vars-vals if
+ 2swap 2drop ( var val vals )
+ set-car!
+ 2drop
+ else
+ env obj@
+ first-frame ( var val frame )
+ add-binding
+ then
+;
+
+hide env
+
+: make-procedure ( params body env -- proc )
+ nil
+ cons cons cons
+ drop compound-proc-type
+;
+
+objvar global-env
+nil nil nil extend-env
+global-env obj!
+
+\ }}}
+
+\ ---- Primitives ---- {{{
+
+: make-primitive ( cfa -- )
+ bl word
+ count
+
+ \ 2dup ." Defining primitive " type ." ..." cr
+
+ cstr>charlist
+ charlist>symbol
+
+ rot primitive-proc-type ( var prim )
+ global-env obj@ define-var
+;
+
+: arg-count-error
+ bold fg red ." Incorrect argument count." reset-term cr
+ abort
+;
+
+: ensure-arg-count ( args n -- )
+ dup 0= if
+ drop nil objeq? false = if
+ arg-count-error
+ then
+ else
+ -rot nil? if
+ arg-count-error
+ then
+
+ cdr rot 1- recurse
+ then
+;
+
+: arg-type-error
+ bold fg red ." Incorrect argument type." reset-term cr
+ abort
+;
+
+: ensure-arg-type ( arg type -- arg )
+ istype? false = if
+ arg-type-error
+ then
+;
+
+
+\ }}}
+
+\ ---- Macros ---- {{{
+
+objvar macro-table
+
+( Look up macro in macro table. Returns nil if
+ no macro is found. )
+: lookup-macro ( name_symbol -- proc )
+ macro-table obj@
+
+ begin
+ nil? false =
+ while
+ 2over 2over
+ car car objeq? if
+ 2swap 2drop
+ car cdr
+ exit
+ then
+
+ cdr
+ repeat
+
+ 2swap 2drop
+;
+
+: make-macro ( name_symbol params body env -- )
+ make-procedure
+
+ 2swap ( proc name_symbol )
+
+ macro-table obj@
+
+ begin
+ nil? false =
+ while
+ 2over 2over ( proc name table name table )
+ car car objeq? if
+ 2swap 2drop ( proc table )
+ car ( proc entry )
+ set-cdr!
+ exit
+ then
+
+ cdr
+ repeat
+
+ 2drop
+
+ 2swap cons
+ macro-table obj@ cons
+ macro-table obj!
+;
+
+\ }}}
+
+\ ---- 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 +! ;
+
+: append-eof
+ 4 parse-str parse-str-span @ + !
+ 1 parse-str-span +! ;
+
+: empty-parse-str
+ 0 parse-str-span !
+ 0 parse-idx ! ;
+
+: getline
+ current-input-port obj@ console-i/o-port obj@ objeq? if
+ parse-str 160 expect cr
+ span @ parse-str-span !
+ else
+ parse-str 160 current-input-port obj@ fileport>fid read-line
+ drop swap parse-str-span !
+
+ parse-str-span @ 0= and if append-eof then
+ then
+ 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 @ + @ ;
+
+: '\t' 9 ;
+: whitespace? ( -- bool )
+ nextchar BL =
+ nextchar '\n' =
+ nextchar '\t' =
+ or or ;
+
+: EOF 4 ;
+: eof? ( -- bool )
+ nextchar EOF = ;
+
+: delim? ( -- bool )
+ whitespace?
+ nextchar [char] ( = or
+ nextchar [char] ) = or
+;
+
+: commentstart? ( -- bool )
+ nextchar [char] ; = ;
+
+: eatspaces
+
+ false \ Indicates whether or not we're eating a comment
+
+ begin
+ dup whitespace? or commentstart? or
+ while
+ dup nextchar '\n' = and if
+ invert \ Stop eating comment
+ else
+ dup false = commentstart? and if
+ invert \ Begin eating comment
+ then
+ then
+
+ inc-parse-idx
+ repeat
+ drop
+;
+
+: digit? ( -- bool )
+ nextchar [char] 0 >=
+ nextchar [char] 9 <=
+ and ;
+
+: minus? ( -- bool )
+ nextchar [char] - = ;
+
+: plus? ( -- bool )
+ nextchar [char] + = ;
+
+: fixnum? ( -- bool )
+ minus? plus? or if
+ inc-parse-idx
+
+ delim? if
+ dec-parse-idx
+ false exit
+ else
+ dec-parse-idx
+ then
+ else
+ digit? false = if
+ false exit
+ then
+ then
+
+ push-parse-idx
+ inc-parse-idx
+
+ begin digit? while
+ inc-parse-idx
+ repeat
+
+ delim? pop-parse-idx
+;
+
+: realnum? ( -- bool )
+ push-parse-idx
+
+ minus? plus? or if
+ inc-parse-idx
+ then
+
+ \ Record starting parse idx:
+ \ Want to detect whether any characters (following +/-) were eaten.
+ parse-idx @
+
+ begin digit? while
+ inc-parse-idx
+ repeat
+
+ [char] . nextchar = if
+ inc-parse-idx
+ begin digit? while
+ inc-parse-idx
+ repeat
+ then
+
+ [char] e nextchar = [char] E nextchar = or if
+ inc-parse-idx
+
+ minus? plus? or if
+ inc-parse-idx
+ then
+
+ digit? invert if
+ drop pop-parse-idx false exit
+ then
+
+ begin digit? while
+ inc-parse-idx
+ repeat
+ then
+
+ \ This is a real number if characters were
+ \ eaten and the next characer is a delimiter.
+ parse-idx @ < delim? and
+
+ pop-parse-idx
+;
+
+: 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] " = ;
+
+: readfixnum ( -- num-atom )
+ plus? minus? or if
+ minus?
+ inc-parse-idx
+ else
+ false
+ then
+
+ 0
+
+ begin digit? while
+ 10 * nextchar [char] 0 - +
+ inc-parse-idx
+ repeat
+
+ swap if negate then
+
+ fixnum-type
+;
+
+: readrealnum ( -- realnum )
+
+ \ Remember that at this point we're guaranteed to
+ \ have a parsable real on this line.
+
+ parse-str parse-idx @ +
+
+ begin delim? false = while
+ inc-parse-idx
+ repeat
+
+ parse-str parse-idx @ + over -
+
+ float-parse
+
+ realnum-type
+;
+
+: readbool ( -- bool-obj )
+ inc-parse-idx
+
+ nextchar [char] f = if
+ false
+ else
+ true
+ then
+
+ inc-parse-idx
+
+ boolean-type
+;
+
+: readchar ( -- char-obj )
+ 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
+;
+
+: 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
+:noname ( -- obj )
+
+ eatspaces
+
+ fixnum? if
+ readfixnum
+ exit
+ then
+
+ realnum? if
+ readrealnum
+ exit
+ then
+
+ boolean? if
+ readbool
+ 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
-vocabulary scheme
-scheme definitions
+ inc-parse-idx
-include term-colours.4th
+ exit
+ then
-0 constant number-type
-1 constant boolean-type
-: istype? ( obj -- obj b )
- over = ;
+ pair? if
+ inc-parse-idx
-\ ---- Read ----
+ eatspaces
-variable parse-idx
-variable dummy-parse-idx
+ readpair
+
+ eatspaces
-: store-parse-idx
- parse-idx @ dummy-parse-idx ! ;
+ nextchar [char] ) <> if
+ bold red ." Missing closing paren." reset-term cr
+ abort
+ then
-: restore-parse-idx
- dummy-parse-idx @ parse-idx ! ;
+ inc-parse-idx
-variable parse-str
+ exit
+ then
-: charavailable? ( -- bool )
- parse-str @ @ parse-idx @ >
+ nextchar [char] ' = if
+ inc-parse-idx
+ quote-symbol recurse nil cons cons exit
+ then
+
+ eof? if
+ EOF character-type
+ inc-parse-idx
+ exit
+ then
+
+ \ Anything else is parsed as a symbol
+ readsymbol charlist>symbol
+
+ \ Replace λ with lambda
+ 2dup λ-symbol objeq? if
+ 2drop lambda-symbol
+ then
+
+
+; is read
+
+\ }}}
+
+\ ---- Eval ---- {{{
+
+: self-evaluating? ( obj -- obj bool )
+ boolean-type istype? if true exit then
+ fixnum-type istype? if true exit then
+ realnum-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
+ none-type istype? if true exit then
+
+ false
;
-: nextchar ( -- char )
- charavailable? if
- parse-str @ 1+ parse-idx @ + @
+: tagged-list? ( obj tag-obj -- obj bool )
+ 2over
+ pair-type istype? false = if
+ 2drop 2drop false
else
- 0
- then
+ car objeq?
+ then ;
+
+: quote? ( obj -- obj bool )
+ quote-symbol tagged-list? ;
+
+: quote-body ( quote-obj -- quote-body-obj )
+ cadr ;
+
+: variable? ( obj -- obj bool )
+ symbol-type istype? ;
+
+: definition? ( obj -- obj bool )
+ define-symbol tagged-list? ;
+
+: make-lambda ( params body -- lambda-exp )
+ lambda-symbol -2rot cons cons ;
+
+( Handles iterative expansion of defines in
+ terms of nested lambdas. Most Schemes only
+ handle one iteration of expansion! )
+: definition-var-val ( obj -- var val )
+
+ cdr 2dup cdr 2swap car ( val var )
+
+ begin
+ symbol-type istype? false =
+ while
+ 2dup cdr 2swap car ( val formals var' )
+ -2rot 2swap ( var' formals val )
+ make-lambda nil cons ( var' val' )
+ 2swap ( val' var' )
+ repeat
+
+ 2swap car
;
-: whitespace? ( -- bool )
- nextchar BL =
- nextchar '\n' = or
+: eval-definition ( obj env -- res )
+ 2dup 2rot ( env env obj )
+ definition-var-val ( env env var val )
+ 2rot eval ( env var val )
+
+ 2rot ( var val env )
+ define-var
+
+ ok-symbol
;
-: delim? ( -- bool )
- whitespace?
- nextchar [char] ( = or
- nextchar [char] ) = or
+: assignment? ( obj -- obj bool )
+ set!-symbol tagged-list? ;
+
+: assignment-var ( obj -- var )
+ cdr car ;
+
+: assignment-val ( obj -- val )
+ cdr cdr car ;
+
+: 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 )
+
+ 2rot ( var val env )
+ set-var
+
+ ok-symbol
;
-: eatspaces
+: macro-definition? ( obj -- obj bool )
+ define-macro-symbol tagged-list? ;
+
+: macro-definition-name ( exp -- mname )
+ cdr car car ;
+
+: macro-definition-params ( exp -- params )
+ cdr car cdr ;
+
+: macro-definition-body ( exp -- body )
+ cdr cdr ;
+
+objvar env
+: eval-define-macro ( obj env -- res )
+ env obj!
+
+ 2dup macro-definition-name 2swap ( name obj )
+ 2dup macro-definition-params 2swap ( name params obj )
+ macro-definition-body ( name params body )
+
+ env obj@ ( name params body env )
+
+ make-macro
+
+ ok-symbol
+;
+hide env
+
+: if? ( obj -- obj bool )
+ if-symbol tagged-list? ;
+
+: if-predicate ( ifobj -- pred )
+ cdr car ;
+
+: if-consequent ( ifobj -- conseq )
+ cdr cdr car ;
+
+: if-alternative ( ifobj -- alt|false )
+ cdr cdr cdr
+ nil? if
+ 2drop false
+ else
+ car
+ then ;
+
+: false? ( boolobj -- boolean )
+ boolean-type istype? if
+ false boolean-type objeq?
+ else
+ 2drop false
+ then
+;
+
+: true? ( boolobj -- bool )
+ false? invert ;
+
+: lambda? ( obj -- obj bool )
+ lambda-symbol tagged-list? ;
+
+: lambda-parameters ( obj -- params )
+ cdr car ;
+
+: lambda-body ( obj -- body )
+ cdr cdr ;
+
+: begin? ( obj -- obj bool )
+ begin-symbol tagged-list? ;
+
+: begin-actions ( obj -- actions )
+ cdr ;
+
+: eval-sequence ( explist env -- finalexp env )
+ ( Evaluates all bar the final expressions in
+ an an expression list. The final expression
+ is returned to allow for tail optimization. )
+
+ 2swap ( env explist )
+
+ \ Abort on empty list
+ nil? if
+ 2drop none
+ 2swap exit
+ then
+
begin
- whitespace?
+ 2dup cdr ( env explist nextexplist )
+ nil? false =
while
- 1 parse-idx +!
+ -2rot car 2over ( nextexplist env exp env )
+ eval
+ 2drop \ discard result
+ 2swap ( env nextexplist )
repeat
+
+ 2drop car 2swap ( finalexp env )
;
-: digit? ( -- bool )
- nextchar [char] 0 >=
- nextchar [char] 9 <=
- and ;
+: application? ( obj -- obj bool )
+ pair-type istype? ;
-: minus? ( -- bool )
- nextchar [char] - = ;
+: operator ( obj -- operator )
+ car ;
-: number? ( -- bool )
- digit? minus? or false = if
- false
- exit
- then
+: operands ( obj -- operands )
+ cdr ;
- store-parse-idx
- 1 parse-idx +!
+: nooperands? ( operands -- bool )
+ nil objeq? ;
- begin digit? while
- 1 parse-idx +!
- repeat
+: first-operand ( operands -- operand )
+ car ;
- delim? charavailable? false = or if
- restore-parse-idx
- true
+: rest-operands ( operands -- other-operands )
+ cdr ;
+
+: list-of-vals ( args env -- vals )
+ 2swap
+
+ 2dup nooperands? if
+ 2swap 2drop
else
- restore-parse-idx
- false
+ 2over 2over first-operand 2swap eval
+ -2rot rest-operands 2swap recurse
+ cons
then
;
-: boolean? ( -- bool )
- nextchar [char] # <> if false exit then
+: procedure-params ( proc -- params )
+ drop pair-type car ;
- 1 parse-idx +!
+: procedure-body ( proc -- body )
+ drop pair-type cdr car ;
- nextchar [char] t <>
- nextchar [char] f <>
- and if 1 parse-idx -! false exit then
+: procedure-env ( proc -- body )
+ drop pair-type cdr cdr car ;
- 1 parse-idx -!
- true
-;
+( Ensure terminating symbol arg name is handled
+ specially to allow for variadic procedures. )
+: flatten-proc-args ( argvals argnames -- argvals' argnames' )
+ nil? if
+ 2over nil? false = if
+ bold fg red ." Too many arguments supplied to compound method. Aborting." reset-term cr
+ abort
+ else
+ 2drop
+ then
+ exit
+ then
-: readnum ( -- num-atom )
- minus? dup if
- 1 parse-idx +!
+ symbol-type istype? if
+ nil cons
+ 2swap
+ nil cons
+ 2swap
+ exit
then
- 0
+ 2over
+ nil? if
+ bold fg red ." Too few arguments supplied to compound method. Aborting." reset-term cr
+ abort
+ else
+ cdr
+ then
- begin digit? while
- 10 * nextchar [char] 0 - +
- 1 parse-idx +!
- repeat
+ 2over cdr
- swap if negate then
+ recurse ( argvals argnames argvals'' argnames'' )
+ 2rot car 2swap cons ( argvals argvals'' argnames' )
+ 2rot car 2rot cons ( argnames' argvals' )
+ 2swap
+;
+
+: apply ( proc argvals -- result )
+ 2swap dup case
+ primitive-proc-type of
+ drop execute
+ endof
+
+ compound-proc-type of
+ 2dup procedure-body ( argvals proc body )
+ -2rot 2dup procedure-params ( body argvals proc argnames )
+ -2rot procedure-env ( body argnames argvals procenv )
- number-type
+ -2rot 2swap
+ flatten-proc-args
+ 2swap 2rot
+
+ extend-env ( body env )
+
+ eval-sequence
+
+ R> drop ['] eval goto-deferred \ Tail call optimization
+ endof
+
+ bold fg red ." Object not applicable. Aborting." reset-term cr
+ abort
+ endcase
;
-: readbool ( -- bool-atom )
- 1 parse-idx +!
+: macro-expand ( proc expbody -- result )
+ 2swap
+ 2dup procedure-body ( expbody proc procbody )
+ -2rot 2dup procedure-params ( procbody expbody proc argnames )
+ -2rot procedure-env ( procbody argnames expbody procenv )
- nextchar [char] f = if
- false
- else
- true
- then
+ -2rot 2swap
+ flatten-proc-args
+ 2swap 2rot
- boolean-type
+ extend-env eval-sequence eval
;
-\ Parse a counted string into a scheme expression
-: read ( -- obj )
+:noname ( obj env -- result )
+ 2swap
- eatspaces
+ self-evaluating? if
+ 2swap 2drop
+ exit
+ then
- number? if
- readnum
+ quote? if
+ quote-body
+ 2swap 2drop
exit
then
- boolean? if
- readbool
+ variable? if
+ 2swap lookup-var
exit
then
- bold fg red ." Error parsing string starting at character '"
- nextchar emit
- ." '. Aborting." reset-term cr
- abort
-;
+ definition? if
+ 2swap eval-definition
+ exit
+ then
-\ ---- Eval ----
+ assignment? if
+ 2swap eval-assignment
+ exit
+ then
-: self-evaluating? ( obj -- obj bool )
- number-type istype? if true exit then
- boolean-type istype? if true exit then
- false ;
+ macro-definition? if
+ 2swap eval-define-macro
+ exit
+ then
-: eval
- self-evaluating? if
+ if? if
+ 2over 2over
+ if-predicate
+ 2swap eval
+
+ true? if
+ if-consequent
+ else
+ if-alternative
+ then
+
+ 2swap
+ ['] eval goto-deferred
+ then
+
+ lambda? if
+ 2dup lambda-parameters
+ 2swap lambda-body
+ 2rot make-procedure
exit
then
+ begin? if
+ begin-actions 2swap
+ eval-sequence
+ ['] eval goto-deferred
+ then
+
+ application? if
+
+ 2over 2over ( env exp env exp )
+ operator ( env exp env opname )
+
+ 2dup lookup-macro nil? false = if
+ \ Macro function evaluation
+
+ ( env exp env opname mproc )
+ 2swap 2drop -2rot 2drop cdr ( env mproc body )
+
+ 2dup print cr
+ macro-expand
+ 2dup print cr
+
+ 2swap
+ ['] eval goto-deferred
+ else
+ \ Regular function application
+
+ 2drop ( env exp env opname )
+
+ 2swap eval ( env exp proc )
+
+ -2rot ( proc env exp )
+ operands 2swap ( proc operands env )
+ list-of-vals ( proc argvals )
+
+ apply
+ exit
+ then
+ then
+
bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
abort
-;
+; is eval
-\ ---- Print ----
+\ }}}
+
+\ ---- Print ---- {{{
+
+: printfixnum ( fixnumobj -- ) drop 0 .R ;
+
+: printrealnum ( realnumobj -- ) drop float-print ;
-: printnum ( numobj -- ) drop . ;
: printbool ( numobj -- )
drop if
." #t"
then
;
-: print ( obj -- )
- ." ;"
- number-type istype? if printnum exit then
+: 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 ;
+
+: printsymbol ( symbolobj -- )
+ nil-type istype? if 2drop exit then
+
+ 2dup car drop emit
+ cdr recurse
+;
+
+: printnil ( nilobj -- )
+ 2drop ." ()" ;
+
+: printpair ( pairobj -- )
+ 2dup
+ car print
+ cdr
+ nil-type istype? if 2drop exit then
+ pair-type istype? if space recurse exit then
+ ." . " print
+;
+
+: printprim ( primobj -- )
+ 2drop ." <primitive procedure>" ;
+
+: printcomp ( primobj -- )
+ 2drop ." <compound procedure>" ;
+
+: printnone ( noneobj -- )
+ 2drop ." Unspecified return value" ;
+
+:noname ( obj -- )
+ fixnum-type istype? if printfixnum exit then
+ realnum-type istype? if printrealnum 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
+ primitive-proc-type istype? if printprim exit then
+ compound-proc-type istype? if printcomp exit then
+ none-type istype? if printnone exit then
+
+ bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
+ abort
+; is print
+
+\ }}}
+
+\ ---- Garbage Collection ---- {{{
+
+variable gc-enabled
+false gc-enabled !
+
+variable gc-stack-depth
+
+: enable-gc
+ depth gc-stack-depth !
+ true gc-enabled ! ;
+
+: disable-gc
+ false gc-enabled ! ;
+
+: gc-enabled?
+ gc-enabled @ ;
+
+: pairlike? ( obj -- obj bool )
+ pair-type istype? if true exit then
+ string-type istype? if true exit then
+ symbol-type istype? if true exit then
+ compound-proc-type istype? if true exit then
+
+ false
;
-\ ---- REPL ----
+: pairlike-marked? ( obj -- obj bool )
+ over nextfrees + @ 0=
+;
+
+: mark-pairlike ( obj -- obj )
+ over nextfrees + 0 swap !
+;
+
+: gc-unmark ( -- )
+ scheme-memsize 0 do
+ 1 nextfrees i + !
+ loop
+;
-create repl-buffer 161 allot
-repl-buffer parse-str !
+: gc-mark-obj ( obj -- )
-: getline
- repl-buffer 1+ 160 expect cr span @ repl-buffer ! ;
+ pairlike? invert if 2drop exit then
+ pairlike-marked? if 2drop exit then
+
+ mark-pairlike
+
+ drop pair-type 2dup
+
+ car recurse
+ cdr recurse
+;
+
+: gc-sweep
+ scheme-memsize nextfree !
+ 0 scheme-memsize 1- do
+ nextfrees i + @ 0<> if
+ nextfree @ nextfrees i + !
+ i nextfree !
+ then
+ -1 +loop
+;
+
+\ Following a GC, this gives the amount of free memory
+: gc-count-marked
+ 0
+ scheme-memsize 0 do
+ nextfrees i + @ 0= if 1+ then
+ loop
+;
+
+\ Debugging word - helps spot memory that is retained
+: gc-zero-unmarked
+ scheme-memsize 0 do
+ nextfrees i + @ 0<> if
+ 0 car-cells i + !
+ 0 cdr-cells i + !
+ then
+ loop
+;
+
+:noname
+ \ ." GC! "
+
+ gc-unmark
+
+ symbol-table obj@ gc-mark-obj
+ macro-table obj@ gc-mark-obj
+ global-env obj@ gc-mark-obj
+
+ depth gc-stack-depth @ do
+ PSP0 i + 1 + @
+ PSP0 i + 2 + @
+
+ gc-mark-obj
+ 2 +loop
+
+ gc-sweep
+
+ \ ." (" gc-count-marked . ." pairs marked as used.)" cr
+; is collect-garbage
-: eof?
- repl-buffer @ 0= if false exit then
- repl-buffer 1+ @ 4 <> if false exit then
- true ;
+\ }}}
+
+\ ---- Loading files ---- {{{
+
+: charlist>cstr ( charlist addr -- n )
+
+ dup 2swap ( origaddr addr charlist )
+
+ begin
+ nil? false =
+ while
+ 2dup cdr 2swap car
+ drop ( origaddr addr charlist char )
+ -rot 2swap ( origaddr charlist addr char )
+ over !
+ 1+ -rot ( origaddr nextaddr charlist )
+ repeat
+
+ 2drop ( origaddr finaladdr )
+ swap -
+;
+
+: load ( addr n -- finalResult )
+ open-input-file
+
+ empty-parse-str
+
+ ok-symbol ( port res )
+
+ begin
+ 2over read-port ( port res obj )
+
+ 2dup EOF character-type objeq? if
+ 2drop 2swap close-port
+ exit
+ then
+
+ 2swap 2drop ( port obj )
+
+ global-env obj@ eval ( port res )
+ again
+;
+
+\ }}}
+
+\ ---- Standard Library ---- {{{
+
+ include scheme-primitives.4th
+
+ \ s" scheme-library.scm" load 2drop
+
+\ }}}
+
+\ ---- REPL ----
: repl
cr ." Welcome to scheme.forth.jl!" cr
." Use Ctrl-D to exit." cr
+ empty-parse-str
+
+ enable-gc
+
begin
- cr bold fg green ." => " reset-term
- getline
+ cr bold fg green ." > " reset-term
+ read-console
- eof? if
- bold fg blue ." Moriturus te saluto." reset-term
+ 2dup EOF character-type objeq? if
+ 2drop
+ bold fg blue ." Moriturus te saluto." reset-term cr
exit
then
- repl-buffer @ 0> if
- 0 parse-idx !
- read
- eval
- fg cyan print reset-term
- then
+ global-env obj@ eval
+
+ fg cyan ." ; " print reset-term
again
;
forth definitions
+
+\ vim:fdm=marker