Continuations objs are pairlike for GC marking.

[scheme.forth.jl.git] / src / scheme.4th

diff --git a/src/scheme.4th b/src/scheme.4th
index 93d2496..9347750 100644 (file)
--- a/src/scheme.4th
+++ b/src/scheme.4th
@@ -530,6 +530,8 @@ global-env obj!
   nil rsp@ 1- rsp0 do
     i 1+ @ fixnum-type 2swap cons
   loop
+
+  rsp@ 1- rsp0 - fixnum-type 2swap cons
 ;
 
 : cons-param-stack ( -- listobj )
@@ -545,13 +547,20 @@ global-env obj!
 
         2swap cons
     2 +loop
+
+  depth 2- 2/ fixnum-type 2swap cons
 ;
 
-: make-continuation
+: make-continuation ( -- continuation true-obj )
+    \ true-obj allows calling code to detect whether
+    \ it is being called immediately following make-continuation
+    \ or by a restore-continuation.
 
   cons-param-stack
   cons-return-stack
   cons drop continuation-type
+
+  true boolean-type
 ;
 
 : continuation->pstack-list
@@ -560,18 +569,74 @@ global-env obj!
 : continuation->rstack-list
   drop pair-type cdr ;
 
-: restore-param-stack ( continuation -- obj_stack continuation )
+: stack-list-len ( stack-list -- n )
+    car drop
+;
 
-  2dup >R >R
+: restore-param-stack ( continuation -- obj_stack )
   continuation->pstack-list
+  2dup >R >R
 
-  ( Idea: allocate stack space first using psp!,
+  ( Allocate stack space first using psp!,
     then copy objects from list. )
+
+  car drop 2*
+  object-stack-base @ psp0 + + psp!
+
+  R> R> 2dup cdr
+  2swap
+  stack-list-len 1- 0 swap do
+
+      2dup car
+      PSP0 object-stack-base @ + i 2* + 2 + !
+      PSP0 object-stack-base @ + i 2* + 1 + !
+      cdr
+
+  -1 +loop
+
+  2drop
+;
+
+: restore-return-stack ( continuation -- )
+
+    continuation->rstack-list
+
+    2dup cdr 2swap stack-list-len ( list n )
+
+    dup RSP0 + RSP! \ expand return stack to accommodate entries
+
+    ( list n )
+
+    1-  \ initial offset n-1
+    0   \ final offset 0
+    swap
+    do
+        2dup cdr 2swap car drop
+        RSP0 i 1+ + !
+    -1 +loop
+
+    2drop
 ;
 
-: restore-continuation
-  \ TODO: replace current parameter and return stacks with
-  \ contents of continuation object.
+: restore-continuation-with-arg ( continuation obj -- )
+
+    >R >R \ Store obj on return stack
+
+    2dup >R >R \ Store copy of continuation on return stack
+
+    restore-param-stack
+
+    R> R> \ Pop continuation from return stack
+
+    R> R> \ Pop obj from return stack
+
+    2swap
+
+    false boolean-type \ Add flag signifying continuation restore
+
+    2swap
+
+    restore-return-stack
 ;
 
 \ }}}
@@ -1717,7 +1782,22 @@ parse-idx-stack parse-idx-sp !
         endof
 
         continuation-type of
-          \ TODO: Apply continuation
+            2swap
+            nil? if
+                except-message: ." Continuations expect exactly 1 argument."
+                recoverable-exception throw
+            then
+
+            2dup cdr
+
+            nil? invert if
+                except-message: ." Continuations expect exactly 1 argument."
+                recoverable-exception throw
+            then
+
+            2drop car
+                
+            restore-continuation-with-arg
         endof
 
         except-message: ." object '" drop print ." ' not applicable." recoverable-exception throw
@@ -2021,6 +2101,7 @@ parse-idx-stack parse-idx-sp !
     symbol-type istype? if true exit then
     compound-proc-type istype? if true exit then
     port-type istype? if true exit then
+    continuation-type istype? if true exit then
 
     false
 ;