make-type symbol-type
make-type primitive-proc-type
make-type compound-proc-type
+make-type continuation-type
make-type port-type
: istype? ( obj type -- obj bool )
over = ;
create cdr-cells scheme-memsize allot
create cdr-type-cells scheme-memsize allot
-variable gc-enabled
-false gc-enabled !
-
-: gc-enabled?
- gc-enabled @ ;
-
create nextfrees scheme-memsize allot
:noname
scheme-memsize 0 do
nextfree !
nextfree @ scheme-memsize >= if
- gc-enabled? if
- collect-garbage
- then
+ collect-garbage
then
nextfree @ scheme-memsize >= if
cdr-cells + !
;
+variable object-stack-base
+: init-object-stack-base
+ depth object-stack-base ! ;
+
: nil 0 nil-type ;
: nil? nil-type istype? ;
: make-frame ( vars vals -- frame )
cons ;
+ : add-frame-to-env ( frame env -- env )
+ cons ;
+
: frame-vars ( frame -- vars )
car ;
;
: extend-env ( vars vals env -- env )
- >R >R
- make-frame
- R> R>
- cons
+ -2rot make-frame
+ 2swap add-frame-to-env
;
- objvar vars
- objvar vals
-
- : get-vars-vals-frame ( var frame -- bool )
- 2dup frame-vars vars obj!
- frame-vals vals obj!
+ : get-vals-frame ( var frame -- vals | nil )
+ 2dup frame-vars
+ 2swap frame-vals ( var vars vals )
begin
- vars obj@ nil objeq? false =
+ nil? false =
while
- 2dup vars obj@ car objeq? if
- 2drop true
+
+ -2rot ( vals var vars )
+ 2over 2over car objeq? if
+ 2drop 2drop
exit
then
- vars obj@ cdr vars obj!
- vals obj@ cdr vals obj!
+ cdr 2rot cdr
repeat
- 2drop false
+ 2drop 2drop 2drop
+ nil
;
- : get-vars-vals ( var env -- vars? vals? bool )
+ : get-vals ( var env -- vals | nil )
begin
nil? false =
while
2over 2over first-frame
- get-vars-vals-frame if
- 2drop 2drop
- vars obj@ vals obj@ true
+ get-vals-frame nil? false = if
+ 2swap 2drop 2swap 2drop
exit
then
+ 2drop
+
enclosing-env
repeat
- 2drop 2drop
- false
+ 2swap 2drop
;
- hide vars
- hide vals
-
- objvar var
-
+ objvar var \ Used only for error messages
: lookup-var ( var env -- val )
2over var obj!
- get-vars-vals if
- 2swap 2drop car
- else
- except-message: ." tried to read unbound variable '" var obj@ print ." '." recoverable-exception throw
+
+ get-vals nil? if
+ except-message: ." tried to read unbound variable '" var obj@ print ." '."
+ recoverable-exception throw
then
+
+ car
;
: set-var ( var val env -- )
- >R >R 2swap R> R> ( val var env )
- 2over var obj!
- get-vars-vals if
- 2swap 2drop ( val vals )
- set-car!
+ 2rot 2dup var obj! ( val env var )
+ 2swap ( val var env )
+ get-vals nil? if
+ except-message: ." tried to set unbound variable '" var obj@ print ." '."
+ recoverable-exception throw
else
- except-message: ." tried to set unbound variable '" var obj@ print ." '." recoverable-exception throw
+ ( val vals )
+ set-car!
then
;
-
hide var
- objvar env
-
: define-var ( var val env -- )
- env obj!
+ first-frame ( var val frame )
+ 2rot 2swap 2over 2over ( val var frame var frame )
- 2over env obj@ ( var val var env )
- get-vars-vals if
- 2swap 2drop ( var val vals )
- set-car!
+ get-vals-frame nil? if
2drop
- else
- env obj@
- first-frame ( var val frame )
+ -2rot 2swap 2rot
add-binding
+ else
+ ( val var frame vals )
+ 2swap 2drop 2swap 2drop
+ set-car!
then
;
- hide env
-
: make-procedure ( params body env -- proc )
nil
cons cons cons
\ }}}
+\ ---- Continuations ---- {{{
+
+: cons-return-stack ( -- listobj )
+ rsp@ 1- rsp0 = if
+ nil exit
+ then
+
+ nil rsp@ 1- rsp0 do
+ i 1+ @ fixnum-type 2swap cons
+ loop
+;
+
+: cons-param-stack ( -- listobj )
+ nil
+
+ depth 2- object-stack-base @ = if
+ exit
+ then
+
+ depth 2- object-stack-base @ do
+ PSP0 i + 1 + @
+ PSP0 i + 2 + @
+
+ 2swap cons
+ 2 +loop
+;
+
+: make-continuation
+
+ cons-param-stack
+ cons-return-stack
+ cons drop continuation-type
+;
+
+: continuation->pstack-list
+ drop pair-type car ;
+
+: continuation->rstack-list
+ drop pair-type cdr ;
+
+: restore-param-stack ( continuation -- obj_stack continuation )
+
+ 2dup >R >R
+ continuation->pstack-list
+
+ ( Idea: allocate stack space first using psp!,
+ then copy objects from list. )
+;
+
+: restore-continuation
+ \ TODO: replace current parameter and return stacks with
+ \ contents of continuation object.
+;
+
+\ }}}
+
\ ---- Primitives ---- {{{
: make-primitive ( cfa -- )
['] evaluate-eproc goto
endof
+ continuation-type of
+ \ TODO: Apply continuation
+ endof
+
except-message: ." object '" drop print ." ' not applicable." recoverable-exception throw
endcase
;
: printcomp ( primobj -- )
2drop ." <compound procedure>" ;
+: printcont ( primobj --)
+ 2drop ." <continuation>" ;
+
: printnone ( noneobj -- )
2drop ." Unspecified return value" ;
pair-type istype? if ." (" printpair ." )" exit then
primitive-proc-type istype? if printprim exit then
compound-proc-type istype? if printcomp exit then
+ continuation-type istype? if printcont exit then
none-type istype? if printnone exit then
port-type istype? if printport exit then
\ ---- Garbage Collection ---- {{{
-variable gc-stack-depth
-
-: enable-gc
- depth gc-stack-depth !
- true gc-enabled ! ;
-
-: disable-gc
- false gc-enabled ! ;
+ ( Notes on garbage collection:
+ This is a mark-sweep garbage collector, invoked by cons.
+ The roots of the object tree used by the marking routine
+ include all objects in the parameter stack, and several
+ other fixed roots such as global-env, symbol-table, macro-table,
+ and the console-i/o-port.
+
+ NO OTHER OBJECTS WILL BE MARKED!
+
+ This places implicit restrictions on when cons can be invoked.
+ Invoking cons when live objects are stored on the return stack
+ or in other variables than the above will result in possible
+ memory corruption if the cons triggers the GC. )
+
+
: pairlike? ( obj -- obj bool )
pair-type istype? if true exit then
string-type istype? if true exit then
console-i/o-port obj@ gc-mark-obj
global-env obj@ gc-mark-obj
- depth gc-stack-depth @ do
+ depth object-stack-base @ do
PSP0 i + 1 + @
PSP0 i + 2 + @
include scheme-primitives.4th
- enable-gc
-
+ init-object-stack-base
s" scheme-library.scm" load 2drop
-
- disable-gc
\ }}}
: repl
empty-parse-str
- enable-gc
+ init-object-stack-base
\ Display welcome message
welcome-symbol nil cons global-env obj@ eval 2drop
throw false
endcase
until
-
- disable-gc
;
forth definitions
The Lambda Lab / projects / scheme.forth.jl.git / commitdiff