Updated README.

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

diff --git a/scheme.4th b/scheme.4th
index 89b3160..1796ea1 100644 (file)
--- a/scheme.4th
+++ b/scheme.4th
@@ -35,17 +35,40 @@ make-type compound-proc-type
 : istype? ( obj type -- obj bool )
     over = ;
 
-\ ------ Cons cell memory ------ {{{
+\ ------ List-structured memory ------ {{{
 
-10000 constant N
-create car-cells N allot
-create car-type-cells N allot
-create cdr-cells N allot
-create cdr-type-cells N allot
+10000 constant scheme-memsize
 
+create car-cells scheme-memsize allot
+create car-type-cells scheme-memsize allot
+create cdr-cells scheme-memsize allot
+create cdr-type-cells scheme-memsize allot
+
+create nextfrees scheme-memsize allot
+:noname
+    scheme-memsize 0 do
+        i 1+ nextfrees i + !
+    loop
+; execute
+        
 variable nextfree
 0 nextfree !
 
+: inc-nextfree
+    nextfrees nextfree @ + @
+    nextfree !
+
+    nextfree @ scheme-memsize >= if
+        collect-garbage
+    then
+
+    nextfree @ scheme-memsize >= if
+        fg red bold
+        ." Out of memory! Aborting."
+        reset-term abort
+    then
+;
+
 : cons ( car-obj cdr-obj -- pair-obj )
     cdr-type-cells nextfree @ + !
     cdr-cells nextfree @ + !
@@ -53,10 +76,7 @@ variable nextfree
     car-cells nextfree @ + !
 
     nextfree @ pair-type
-
-    1 nextfree +!
-
-    collect-garbage
+    inc-nextfree
 ;
 
 : car ( pair-obj -- car-obj )
@@ -119,27 +139,6 @@ variable nextfree
 
 \ }}}
 
-\ ---- Garbage Collection ---- {{{
-
-variable gc-enabled
-false gc-enabled !
-
-: gc-enable
-    true gc-enabled ! ;
-
-: gc-disable
-    false gc-enabled ! ;
-
-: gc-enabled?
-    gc-enabled @ ;
-
-:noname 
-    gc-enabled? if
-        .s ." GC!" cr
-    then
-; is collect-garbage
-
-\ }}}
 
 \ ---- Pre-defined symbols ---- {{{
 
@@ -691,7 +690,7 @@ parse-idx-stack parse-idx-sp !
     realnum-type
 ;
 
-: readbool ( -- bool-atom )
+: readbool ( -- bool-obj )
     inc-parse-idx
     
     nextchar [char] f = if
@@ -705,7 +704,7 @@ parse-idx-stack parse-idx-sp !
     boolean-type
 ;
 
-: readchar ( -- char-atom )
+: readchar ( -- char-obj )
     inc-parse-idx
     inc-parse-idx
 
@@ -1244,6 +1243,109 @@ parse-idx-stack parse-idx-sp !
 
 \ }}}
 
+\ ---- Garbage Collection ---- {{{
+
+variable gc-enabled
+false gc-enabled !
+
+variable gc-stack-depth
+
+: enable-gc
+    depth gc-stack-depth !
+    true gc-enabled ! ;
+
+: disable-gc
+    false gc-enabled ! ;
+
+: gc-enabled?
+    gc-enabled @ ;
+
+: pairlike? ( obj -- obj bool )
+    pair-type istype? if true exit then
+    string-type istype? if true exit then
+    symbol-type istype? if true exit then
+    compound-proc-type istype? if true exit then
+
+    false
+;
+
+: pairlike-marked? ( obj -- obj bool )
+    over nextfrees + @ 0=
+;
+
+: mark-pairlike ( obj -- obj )
+        over nextfrees + 0 swap !
+;
+
+: gc-unmark ( -- )
+    scheme-memsize 0 do
+        1 nextfrees i + !
+    loop
+;
+
+: gc-mark-obj ( obj -- )
+
+    pairlike? invert if 2drop exit then
+    pairlike-marked? if 2drop exit then
+
+    mark-pairlike
+
+    drop pair-type 2dup
+
+    car recurse
+    cdr recurse
+;
+
+: gc-sweep
+    scheme-memsize nextfree !
+    0 scheme-memsize 1- do
+        nextfrees i + @ 0<> if
+            nextfree @ nextfrees i + !
+            i nextfree !
+        then
+    -1 +loop
+;
+
+\ Following a GC, this gives the amount of free memory
+: gc-count-marked
+    0
+    scheme-memsize 0 do
+        nextfrees i + @ 0= if 1+ then
+    loop
+;
+
+\ Debugging word - helps spot memory that is retained
+: gc-zero-unmarked
+    scheme-memsize 0 do
+        nextfrees i + @ 0<> if
+            0 car-cells i + !
+            0 cdr-cells i + !
+        then
+    loop
+;
+
+:noname
+    \ ." GC! "
+
+    gc-unmark
+
+    symbol-table obj@ gc-mark-obj
+    global-env obj@ gc-mark-obj
+
+    depth gc-stack-depth @ do
+        PSP0 i + 1 + @
+        PSP0 i + 2 + @
+
+        gc-mark-obj
+    2 +loop
+
+    gc-sweep
+
+    \ ." (" gc-count-marked . ." pairs marked as used.)" cr
+; is collect-garbage
+
+\ }}}
+
 \ ---- REPL ----
 
 : repl
@@ -1253,7 +1355,7 @@ parse-idx-stack parse-idx-sp !
     
     empty-parse-str
 
-    gc-enable
+    enable-gc
 
     begin
         cr bold fg green ." > " reset-term