Simplify LOAD's INTERPRET exit mechanism

This should allow me to simplify LOAD's exit mechanism on block
end.

blk/044

@@ -2,4 +2,3 @@ INTERPRET --   Get a line from stdin, compile it in tmp memory,
                then execute the compiled contents.
 LEAVE     --   In a DO..LOOP, exit at the next LOOP call.
 QUIT      --   Return to interpreter prompt immediately
-EXIT!     --   Exit current INTERPRET loop.

blk/062

@@ -1,5 +1,7 @@
 WORD    -- a   Read one word from buffered input and push its
-               addr.
+               addr. Always null terminated. If ASCII EOT is
+               encountered, a will point to it (it is cons-
+               idered a word).
 There are also ascii const emitters:
 BS CR LF SPC CRLF
 NL is an indirect word (see B80) that aliases to CRLF by

blk/405

@@ -1,9 +1,7 @@
 : WS? 33 < ;
+: EOT? 4 = ; ( 4 == ASCII EOT, CTRL+D )
 
 : TOWORD
-    BEGIN
-        C< DUP WS? NOT IF EXIT THEN DROP
-    AGAIN
-;
-
-
+    0 ( dummy ) BEGIN
+        DROP C< DUP WS? NOT OVER EOT? OR
+    UNTIL ;

blk/406

@@ -1,16 +1,13 @@
 ( Read word from C<, copy to WORDBUF, null-terminate, and
   return WORDBUF. )
 : WORD
-    0x0e RAM+  ( 0e == WORDBUF )
-    TOWORD     ( a c )
+    0x0e RAM+ TOWORD ( a c )
+    DUP EOT? IF OVER ! EXIT THEN
     BEGIN
         ( We take advantage of the fact that char MSB is
           always zero to pre-write our null-termination )
-        OVER ! 1+            ( a+1 )
-        C<                   ( a c )
+        OVER ! 1+ C< ( a c )
         OVER 0x2d ( 2e-1 for NULL ) RAM+ = OVER WS? OR
-    UNTIL
-    ( a this point, PS is: a WS )
-    ( null-termination is already written )
-    2DROP
-    0x0e RAM+ ;
+    UNTIL ( a c )
+    SWAP DROP 0x0e RAM+ ( ws a )
+    SWAP EOT? IF 4 OVER ! THEN ;

blk/409

@@ -1,16 +1,7 @@
 : INTERPRET
     BEGIN
-    WORD
+    WORD DUP C@ EOT? IF DROP EXIT THEN
     (find)
     NOT IF (parse) ELSE EXECUTE THEN
     C<? NOT IF LIT< (ok) (find) IF EXECUTE THEN THEN
     AGAIN ;
-
-( Drop RSP until I-2 == INTERPRET. )
-: EXIT!
-    ['] INTERPRET       ( I )
-    BEGIN               ( I )
-    DUP                 ( I I )
-    R> DROP I 2- @      ( I I a )
-    = UNTIL
-    DROP ;

blk/411

@@ -9,6 +9,5 @@
     ['] (boot<) 0x0c RAM+ !
     ( boot< always has a char waiting. 06 == C<?* )
     1 0x06 RAM+ !
-    INTERPRET
-;
+    INTERPRET BYE ;
 

blk/429

@@ -1,8 +1,8 @@
 ( Read one line in input buffer and make IN> point to it )
 : (rdln)
-    (infl) BEGIN (rdlnc) NOT UNTIL
+    ( EOT or less triggers line flush )
+    (infl) BEGIN (rdlnc) 5 < UNTIL
     LF IN( IN> ! ;
-
 ( And finally, implement C<* )
 : RDLN<
     IN> @ C@

blk/432

@@ -1,14 +1,3 @@
-: _
-    (boot<)
-    DUP 4 = IF
-        ( We drop our char, but also "a" from WORD: it won't
-          have the opportunity to balance PSP because we're
-          EXIT!ing. )
-        2DROP
-        ( We're finished interpreting )
-        EXIT!
-    THEN
-;
 ( pre-comment for tight LOAD: The 0x08==I check after INTERPRET
   is to check whether we're restoring to "_", the word above.
   if yes, then we're in a nested load. Also, the 1 in 0x06 is

blk/433

@@ -5,7 +5,7 @@
     0x2e RAM+ @ >R  ( boot ptr )
     BLK@
     BLK( 0x2e RAM+ ! ( Point to beginning of BLK )
-    ['] _ 0x08 RAM+ ! 
+    ['] (boot<) 0x08 RAM+ !
     1 0x06 RAM+ !  ( 06 == C<? )
     INTERPRET
     R> 0x2e RAM+ ! R> 0x06 RAM+ !

emul/forth.c

@@ -17,7 +17,6 @@
 #define BLK_PORT 0x03
 #define BLKDATA_PORT 0x04
 
-static int running;
 static FILE *fp;
 static FILE *blkfp;
 static int retcode = 0;
@@ -27,18 +26,14 @@ static uint8_t iord_stdio()
 {
     int c = getc(fp);
     if (c == EOF) {
-        running = 0;
+        c = 4; // ASCII EOT
     }
     return (uint8_t)c;
 }
 
 static void iowr_stdio(uint8_t val)
 {
-    if (val == 0x04) { // CTRL+D
-        running = 0;
-    } else {
     putchar(val);
-    }
 }
 
 static void iowr_ret(uint8_t val)
@@ -123,9 +118,7 @@ int main(int argc, char *argv[])
     }
 
     // Run!
-    running = 1;
-
-    while (running && emul_step());
+    while (emul_step());
 
     if (tty) {
         printf("\nDone!\n");