Support nested LOAD

blk/044

@@ -1,3 +1,4 @@
 (cont.)
 UNTIL     f --         *I* Jump backwards to BEGIN if f is
                        false.
+EXIT!     --           Exit current INTERPRET loop.

blk/103

@@ -0,0 +1 @@
+42 . 102 LOAD 43 .

forth/blk.fs

@@ -7,14 +7,12 @@
 : BLK!* 2 BLKMEM+ ;
 ( Current blk pointer in ( )
 : BLK> 4 BLKMEM+ ;
-( backup for CINPTR when LOADing )
-: BLKC<* 6 BLKMEM+ ;
-: BLK( 8 BLKMEM+ ;
+: BLK( 6 BLKMEM+ ;
 
 : BLK$
     H@ 0x57 RAM+ !
-    ( 1024 for the block, 8 for variables )
-    1032 ALLOT
+    ( 1024 for the block, 6 for variables )
+    1030 ALLOT
     ( LOAD detects end of block with ASCII EOT. This is why
       we write it there. EOT == 0x04 )
     4 C,
@@ -42,17 +40,33 @@
     DUP 4 = IF
         DROP
         ( We're finished interpreting )
-        BLKC<* @ 0x0c RAM+ !
-        C<
+        EXIT!
     THEN
 ;
 
 : LOAD
+    ( save BLK>, CINPTR and boot< ptr to RSP )
+    BLK> @ >R
+    0x0c RAM+ @ >R
+    0x2e RAM+ @ >R
     BLK@
-    ( 2e == BOOT C< PTR )
+    ( Point to beginning of BLK )
     BLK( 0x2e RAM+ !
-    ( Save current C< ptr )
-    0x0c RAM+ @ BLKC<* !
     ( 0c == CINPTR )
     ['] _ 0x0c RAM+ !
+    INTERPRET
+    R> 0x2e RAM+ !
+    ( Before we restore CINPTR, are we restoring it to "_"?
+      if yes, it means we're in a nested LOAD which means we
+      should also load back the saved BLK>. Otherwise, we can
+      ignore the BLK> from RSP. )
+    I 0x0c RAM+ @ = IF
+        ( nested load )
+        R> DROP ( CINPTR )
+        R> BLK@
+    ELSE
+        ( not nested )
+        R> 0x0c RAM+ !
+        R> DROP ( BLK> )
+    THEN
 ;

forth/core.fs

@@ -149,3 +149,12 @@
     LIT< _sys (find) NOT IF ABORT THEN
     DUP HERE ! CURRENT !
 ;
+
+( Drop RSP until I-2 == INTERPRET. )
+: EXIT!
+    ['] INTERPRET       ( I )
+    BEGIN               ( I )
+    DUP                 ( I I )
+    R> DROP I 2 - @     ( I I a )
+    = UNTIL
+;