X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fscheme.4th;h=e94796c550ef26630bb7ab426c42a4f58716b225;hb=1611b5484902b38774e0e61b84a14868dcc30152;hp=9f744c0b9a6224bf12b99e928e62fbe71b5ac488;hpb=96ce36055ecce6550bfac3ffbc60a2de331c9e85;p=scheme.forth.jl.git

diff --git a/src/scheme.4th b/src/scheme.4th
index 9f744c0..e94796c 100644
--- a/src/scheme.4th
+++ b/src/scheme.4th
@@ -39,6 +39,7 @@ make-type pair-type
 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 = ;
@@ -75,12 +76,6 @@ create car-type-cells scheme-memsize allot
 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
@@ -96,9 +91,7 @@ variable nextfree
     nextfree !
 
     nextfree @ scheme-memsize >= if
-        gc-enabled? if
-            collect-garbage
-        then
+      collect-garbage
     then
 
     nextfree @ scheme-memsize >= if
@@ -140,6 +133,10 @@ variable nextfree
     cdr-cells + !
 ;
 
+variable object-stack-base
+: init-object-stack-base
+  depth object-stack-base ! ;
+
 : nil 0 nil-type ;
 : nil? nil-type istype? ;
 
@@ -529,6 +526,62 @@ global-env obj!
 
 \ }}}
 
+\ ---- 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 -- )
@@ -1669,6 +1722,10 @@ parse-idx-stack parse-idx-sp !
                ['] evaluate-eproc goto
         endof
 
+        continuation-type of
+          \ TODO: Apply continuation
+        endof
+
         except-message: ." object '" drop print ." ' not applicable." recoverable-exception throw
     endcase
 ;
@@ -1917,6 +1974,9 @@ parse-idx-stack parse-idx-sp !
 : printcomp ( primobj -- )
     2drop ." <compound procedure>" ;
 
+: printcont ( primobj --)
+    2drop ." <continuation>" ;
+
 : printnone ( noneobj -- )
     2drop ." Unspecified return value" ;
 
@@ -1935,6 +1995,7 @@ parse-idx-stack parse-idx-sp !
     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
 
@@ -1945,15 +2006,6 @@ parse-idx-stack parse-idx-sp !
 
 \ ---- Garbage Collection ---- {{{
 
-variable gc-stack-depth
-
-: enable-gc
-    depth gc-stack-depth !
-    true gc-enabled ! ;
-
-: disable-gc
-    false gc-enabled ! ;
-
 : pairlike? ( obj -- obj bool )
     pair-type istype? if true exit then
     string-type istype? if true exit then
@@ -2029,7 +2081,7 @@ variable gc-stack-depth
     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 + @
 
@@ -2078,11 +2130,8 @@ variable gc-stack-depth
 
     include scheme-primitives.4th
 
-    enable-gc
-
+    init-object-stack-base
     s" scheme-library.scm" load 2drop
-
-    disable-gc
     
 \ }}}
 
@@ -2110,7 +2159,7 @@ variable gc-stack-depth
 : repl
     empty-parse-str
 
-    enable-gc
+    init-object-stack-base
 
     \ Display welcome message
     welcome-symbol nil cons global-env obj@ eval 2drop
@@ -2124,8 +2173,6 @@ variable gc-stack-depth
             throw false
         endcase
     until
-
-    disable-gc
 ;
 
 forth definitions