: istype? ( obj type -- obj bool )
over = ;
-\ ------ Memory ------
+\ ------ Cons cell memory ------
-100 constant N
+1000 constant N
create car-cells N allot
create car-type-cells N allot
create cdr-cells N allot
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? ;
-: objvar create 0 , 0 , ;
+: objvar create nil swap , , ;
: value@ ( objvar -- val ) @ ;
: type@ ( objvar -- type ) 1+ @ ;
: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ;
: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ;
+: objeq? ( obj obj -- bool )
+ rot = -rot = and ;
+
+\ ---- Pre-defined symbols ----
+
objvar symbol-table
-nil symbol-table setobj
+
+: (create-symbol) ( addr n -- symbol-obj )
+ dup 0= if
+ 2drop nil
+ else
+ 2dup drop @ character-type 2swap
+ swap 1+ swap 1-
+ recurse
+
+ cons
+ then
+;
+
+: create-symbol ( -- )
+ bl word
+ count
+
+ (create-symbol)
+ drop symbol-type
+
+ 2dup
+
+ symbol-table fetchobj
+ cons
+ symbol-table setobj
+
+ create swap , ,
+ does> dup @ swap 1+ @
+;
+
+create-symbol quote quote-symbol
+create-symbol define define-symbol
+create-symbol set! set!-symbol
+
+\ ---- Environments ----
+
+objvar global-env
+
+: 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-car!
+ 2swap 2over frame-vars cons
+ swap set-cdr!
+;
+
+: extend-env ( vars vals env -- env )
+ >R >R
+ make-frame
+ R> R>
+ cons
+;
+
+objvar vars
+objvar vals
+
+: lookup-var-frame ( var frame -- val? bool )
+ 2dup frame-vars vars setobj
+ frame-vals vals setobj
+
+ begin
+ vars fetchobj nil objeq? false =
+ while
+ 2dup vars fetchobj car objeq? if
+ 2drop
+ vals fetchobj car true
+ exit
+ then
+
+ vars fetchobj cdr vars setobj
+ vals fetchobj cdr vals setobj
+ repeat
+
+ 2drop false
+;
+
+: lookup-var ( var env -- val )
+ begin
+ 2dup nil objeq? false =
+ while
+ 2over 2over first-frame
+ lookup-var-frame if
+ -rot 2drop -rot 2drop
+ exit
+ then
+
+ enclosing-env
+ repeat
+
+ 2drop
+ bold fg red ." Unbound variable " print ." . Aborting." reset-term cr
+ abort
+;
\ ---- Read ----
: 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
if
nil? -rot 2drop
if
- true exit
+ 2drop 2drop true exit
else
- false exit
+ 2drop 2drop false exit
then
else
nil? -rot 2drop
if
- false exit
+ 2drop 2drop false exit
then
then
2over 2over
\ Neither nil
- car 2swap car rot = -rot = and if
+ car drop -rot car drop = if
cdr 2swap cdr recurse
else
2drop 2drop false
then
;
-: (symbol-in-table?) ( charlist symbol-table -- charlist symbol-obj )
+: charlist>symbol ( charlist -- symbol-obj )
+
+ symbol-table fetchobj
begin
nil? false =
while
2over 2over
- car
+ car drop pair-type
charlist-equiv if
+ 2swap 2drop
+ car
+ exit
+ else
+ cdr
+ then
repeat
-;
-: symbol-in-table? ( charlist -- charlist bool )
- symbol-table (symbol-in-table?) ;
+ 2drop
+ drop symbol-type 2dup
+ symbol-table fetchobj cons
+ symbol-table setobj
+;
defer read
-: readpair ( -- obj )
+: readpair ( -- pairobj )
eatspaces
\ Empty lists
exit
then
- symbol? if
- readsymbol
- drop symbol-type
- 2dup
- symbol-table fetch
- cons
- symbol-table set
- exit
- then
-
pair? if
inc-parse-idx
exit
then
+ nextchar [char] ' = if
+ inc-parse-idx
+ quote-symbol recurse nil cons cons exit
+ then
+
eof? if
bold fg blue ." Moriturus te saluto." reset-term ." ok" cr
quit
then
- bold fg red ." Error parsing string starting at character '"
- nextchar emit
- ." '. Aborting." reset-term cr
- abort
+ \ Anything else is assumed to be a symbol
+ readsymbol charlist>symbol
; is read
\ ---- Eval ----
: self-evaluating? ( obj -- obj bool )
- true \ everything self-evaluating for now
+ boolean-type istype? if true exit then
+ number-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
+: tagged-list? ( obj tag-obj -- obj bool )
+ 2over
+ pair-type istype? false = if
+ 2drop 2drop false
+ else
+ car objeq?
+ then ;
+
+: quote? ( obj -- obj bool )
+ quote-symbol tagged-list? ;
+
+: quote-body ( quote-obj -- quote-body-obj )
+ cadr ;
+
+: eval ( obj env -- result )
+ 2swap
+
self-evaluating? if
+ 2swap 2drop
+ exit
+ then
+
+ quote? if
+ quote-body
+ 2swap 2drop
exit
then
begin
cr bold fg green ." > " reset-term
read
- eval
+ global-env fetchobj eval
fg cyan ." ; " print reset-term
again
;
The Lambda Lab / projects / scheme.forth.jl.git / blobdiff