+\ ---- Continuations ---- {{{
+
+: cons-return-stack ( -- listobj )
+ rsp@ 1- rsp0 = if
+ nil exit
+ then
+
+ nil rsp@ 1- rsp0 do
+ i 1+ @ fixnum-type 2swap cons
+ loop
+
+ rsp@ 1- rsp0 - fixnum-type 2swap cons
+;
+
+: 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
+
+ depth 2- fixnum-type 2swap cons
+;
+
+: 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->pstack-list
+ 2dup >R >R
+
+ ( Allocate stack space first using psp!,
+ then copy objects from list. )
+
+ car drop
+ object-stack-base @ psp0 + + psp!
+
+ R> R> 2dup cdr
+ 2swap
+ car drop 2- 0 swap do
+
+ 2dup car
+ PSP0 object-stack-base @ + i + 2 + !
+ PSP0 object-stack-base @ + i + 1 + !
+ cdr
+
+ -2 +loop
+
+ 2drop
+;
+
+: list->pad ( list -- n )
+
+ 2dup car drop -rot \ keep length of list on stack
+ 2dup cdr 2swap car drop \ get length from list
+
+ pad + 1- \ final dest addr
+ pad \ initial dest addr
+ swap
+ do
+ 2dup cdr 2swap car
+ drop i !
+ -1 +loop
+
+ 2drop
+;
+
+: restore-return-stack ( continuation -- )
+
+ trace
+
+ continuation->rstack-list
+ list->pad
+ dup
+ RSP0 + RSP! \ expand return stack to accommodate entries
+
+ 0 \ initial offset
+ do
+ pad i + @ RSP0 i 1+ + !
+ loop
+
+ trace
+;
+
+: restore-continuation ( continuation -- )
+ \ TODO: replace current parameter and return stacks with
+ \ contents of continuation object.
+
+ 2dup >R >R
+ restore-param-stack
+
+ ." ====== PARAM STACK RESTORED ======" cr
+ trace
+
+ R> R>
+ restore-return-stack
+;
+
+\ }}}
+