4 constant nil-type
5 constant pair-type
6 constant symbol-type
+7 constant primitive-type
: 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 ;
+
+: 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>
+;
+
+\ }}}
+
+\ ---- Pre-defined symbols ---- {{{
+
objvar symbol-table
-nil symbol-table setobj
-\ ---- Read ----
+: (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
+create-symbol ok ok-symbol
+create-symbol if if-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 setobj
+ frame-vals vals setobj
+
+ begin
+ vars fetchobj nil objeq? false =
+ while
+ 2dup vars fetchobj car objeq? if
+ 2drop true
+ exit
+ then
+
+ vars fetchobj cdr vars setobj
+ vals fetchobj cdr vals setobj
+ repeat
+
+ 2drop false
+;
+
+: get-vars-vals ( var env -- vars? vals? bool )
+
+ begin
+ 2dup nil objeq? false =
+ while
+ 2over 2over first-frame
+ get-vars-vals-frame if
+ 2drop 2drop
+ vars fetchobj vals fetchobj 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 setobj
+
+ 2over env fetchobj ( var val var env )
+ get-vars-vals if
+ 2swap 2drop ( var val vals )
+ set-car!
+ 2drop
+ else
+ env fetchobj
+ first-frame ( var val frame )
+ add-binding
+ then
+;
+
+hide env
+
+objvar global-env
+nil nil nil extend-env
+global-env setobj
+
+\ }}}
+
+\ ---- Primitives ---- {{{
+
+: make-primitive ( cfa -- )
+ bl word
+ count
+
+ (create-symbol)
+ drop symbol-type
+
+ 2dup
+
+ symbol-table fetchobj
+ cons
+ symbol-table setobj
+
+ rot primitive-type ( var prim )
+ global-env fetchobj define-var
+;
+
+: add-prim ( args -- )
+ 2dup nil objeq? if
+ 2drop
+ 0 number-type
+ else
+ 2dup cdr recurse drop
+ -rot car drop
+ + number-type
+ then
+;
+
+' add-prim make-primitive +
+
+\ }}}
+
+\ ---- Read ---- {{{
+
+defer read
variable parse-idx
variable stored-parse-idx
: 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
symbol-table setobj
;
-defer read
-
: readpair ( -- pairobj )
eatspaces
string? if
inc-parse-idx
+
readstring
drop string-type
then
inc-parse-idx
- exit
- then
- symbol? if
- readsymbol charlist>symbol
exit
then
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 parsed as a symbol
+ readsymbol charlist>symbol
; is read
-\ ---- Eval ----
+\ }}}
+
+\ ---- Eval ---- {{{
+
+defer 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
+;
+
+: 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 ;
+
+: variable? ( obj -- obj bool )
+ symbol-type istype? ;
+
+: definition? ( obj -- obj bool )
+ define-symbol tagged-list? ;
+
+: definition-var ( obj -- var )
+ cdr car ;
+
+: definition-val ( obj -- val )
+ cdr cdr car ;
+
+: assignment? ( obj -- obj bool )
+ set!-symbol tagged-list? ;
+
+: assignment-var ( obj -- var )
+ cdr car ;
+
+: assignment-val ( obj -- val )
+ cdr cdr car ;
+
+: eval-definition ( obj env -- res )
+ 2swap
+ 2over 2over ( env obj env obj )
+ definition-val 2swap ( env obj valexp env )
+ eval ( env obj val )
+
+ 2swap definition-var 2swap ( env var val )
+
+ 2rot ( var val env )
+ define-var
+
+ ok-symbol
+;
+
+: 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
+;
+
+: 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
+ 2dup nil objeq? 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 ;
+
+: application? ( obj -- obj bool)
+ pair-type istype? ;
+
+: operator ( obj -- operator )
+ car ;
+
+: operands ( obj -- operands )
+ cdr ;
+
+: nooperands? ( operands -- bool )
+ nil objeq? ;
+
+: first-operand ( operands -- operand )
+ car ;
+
+: rest-operands ( operands -- other-operands )
+ cdr ;
+
+: list-of-vals ( args env -- vals )
+ 2swap
+
+ 2dup nooperands? if
+ 2swap 2drop
+ else
+ 2over 2over first-operand 2swap eval
+ -2rot rest-operands 2swap recurse
+ cons
+ then
;
-: eval
+:noname ( obj env -- result )
+ 2swap
+
self-evaluating? if
+ 2swap 2drop
+ exit
+ then
+
+ quote? if
+ quote-body
+ 2swap 2drop
+ exit
+ then
+
+ variable? if
+ 2swap lookup-var
+ exit
+ then
+
+ definition? if
+ 2swap eval-definition
+ exit
+ then
+
+ assignment? if
+ 2swap eval-assignment
+ exit
+ then
+
+ if? if
+ 2over 2over
+ if-predicate
+ 2swap eval
+
+ true? if
+ if-consequent
+ else
+ if-alternative
+ then
+
+ 2swap ['] eval goto
+ then
+
+ application? if
+ 2over 2over
+ operator 2swap eval
+
+ primitive-type istype? false = if
+ bold fg red ." Object not applicable. Aboring." reset-term cr
+ abort
+ then
+
+ -2rot
+ operands 2swap list-of-vals
+
+ 2swap drop execute
exit
then
bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
abort
-;
+; is eval
+
+\ }}}
-\ ---- Print ----
+\ ---- Print ---- {{{
+
+defer print
: printnum ( numobj -- ) drop 0 .R ;
: printnil ( nilobj -- )
2drop ." ()" ;
-defer print
: printpair ( pairobj -- )
2dup
car print
." . " print
;
+: printprim ( primobj -- )
+ 2drop ." <primitive procedure>" ;
+
:noname ( obj -- )
number-type istype? if printnum exit then
boolean-type istype? if printbool exit then
symbol-type istype? if printsymbol exit then
nil-type istype? if printnil exit then
pair-type istype? if ." (" printpair ." )" exit then
+ primitive-type istype? if printprim exit then
bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
abort
; is print
+\ }}}
+
\ ---- REPL ----
: repl
begin
cr bold fg green ." > " reset-term
read
- eval
+ global-env fetchobj eval
fg cyan ." ; " print reset-term
again
;
forth definitions
+
+\ vim:fdm=marker
The Lambda Lab / projects / scheme.forth.jl.git / blobdiff