Merge pull request #2 from RevCurtisP/break-case

Modified BREAK to exit CASE blocks

doc/c02.txt

@@ -525,10 +525,10 @@ When using the select keyword, it is followed by an expression (surrounded
 by parenthesis) and an opening curly brace, which begins the select block.
 This must then be followed by a case statement.
 
-Each use of the case keyword is followed by term and a colon. If the 
-term is equal to select expression then the code immediately following 
-the is executed, otherwise, program execution transfers to the next 
-case or default statement. 
+Each use of the case keyword is followed by one or more comma-separated
+terms and a colon. If the term is equal to select expression then the 
+code immediately following the is executed, otherwise, program execution 
+transfers to the next case or default statement. 
 
 The code between two case statements or a case and default statement is
 called a case block. At the end of a case block, program execution
@@ -541,16 +541,48 @@ default statement and the end of the select block (marked with a closing
 curly-brace) is called the default block and is executed if none of
 the case arguments matched the select expression.
 
+If the constant 0 is to be used as an argument to any of the case 
+statements, using it as the first argument of the first case statement 
+will produce slightly more efficient code.
+
 Example:
   puts("You pressed ");
   select (getc()) {
+    case $00: putln("Nothing");
     case $0D: putln("The Enter key");
     case ' ': putln("The space bar");
+    case 'A','a': putln ("The letter A");
     case ltr: putln("The character in variable 'ltr'");
     case s[2]: putln("The third character of string 's'"); 
     default: putln("some other key");
   }
 
+Unlike the switch statement in C, the break statement is not needed to 
+exit from a case block. It may be used, however, to prematurely exit a 
+case block if desired.
+
+Example:
+  select (arg) {
+    case foo: 
+      puts("fu");
+      if (!bar) break;
+      puts("bar");
+    default: //do nothing
+  }
+
+In addition, fall through of case blocks can be duplicated using the goto
+statement with a label.
+
+  select (num)
+    case 1:
+      putc('I');
+      goto two;
+    case 2:
+    two: 
+      putc('I');
+    default: //do nothing
+   }
+
 Note: It's possible for multiple case statement arguments to evaluate to
 the same value. In this case, only the first case block matching the
 select expression will be executed.

label.c

@@ -13,20 +13,21 @@
 #include "parse.h"
 #include "label.h"
 
+const char lblflg[] = {LFNONE, LFNONE, LFBGN, LFEND, LFBGN, LFEND, LFEND, LFNONE, LFNONE}; //Label Type Flags
+
 /* Find Last Label of Specified Types *
  * Args: lbtyp1: First label type     *
  *       lbtyp2: Second label type    *
  * Sets: tmplbl - Label name          *
  * Returns: Index into label table    *
  *          (-1 if not found)         */
-int lstlbl(int lbtyp1, int lbtyp2)
+int lstlbl(int lbflag)
 {
   int i;
-  DEBUG("Searching for label type %d ", lbtyp1);
-  DEBUG("and label type %d\n",lbtyp2);
+  DEBUG("Searching for label flag %d\n", lbflag);
   for (i = lblcnt - 1; i>-1; i--) {
-    if (lbltyp[i] == lbtyp1) break;
-    if (lbltyp[i] == lbtyp2) break;
+    //DEBUG("Comparing against flag %d", lblflg[lbltyp[i]]); 
+    if (lblflg[lbltyp[i]] == lbflag) break;
   }
   DEBUG("Search produced label index %d\n", i);
   if (i>=0) 

label.h

@@ -19,6 +19,7 @@ int  lblnxt;                       //Sequence of next label to be generated
 char lbltmp[LABLEN+1];             //Label Temporary Storage
 
 enum ltypes {LTNONE, LTIF, LTLOOP, LTEND, LTDO, LTDWHL, LTSLCT, LTCASE, LTFUNC}; //Label Types
+enum lflags {LFNONE, LFBGN, LFEND}; //Label Flag Types
 
 void prslbl();              //Parse Label From Code
 void newlbl(char* lbname);  //Generate New Block Label

py65/testslct.c02

@@ -39,7 +39,8 @@ for (c=0; c<10; c++) {
 }
 
 newlin();
-for (c=$18; c<$23; c++) {
+for (c=$18; c<$22; c++) {
+  if (c & 15 > 9) continue; //Skip $1A - $1F 
   prbyte(c);
   putc(' ');
   select (c) {
@@ -48,8 +49,8 @@ for (c=$18; c<$23; c++) {
       putln("BREAK ONE-NINE");
       if (c==$19) break;
       putln("OOPS!");
-    case $22: putln("BLACKJACK!");
-    default: //putln("*");
+    case $21: putln("BLACKJACK!");
+    default: putln("*");
   }
 }
 

stmnt.c

@@ -139,10 +139,10 @@ void prsasn(char trmntr)
 }
 
 /* parse and compile 'break'/'continue' statement */
-void pbrcnt(int lbtyp1, int lbtyp2) 
+void pbrcnt(int lbflag) 
 {
   DEBUG("Parsing BREAK/CONTINUE statement\n", 0);
-  if (lstlbl(lbtyp1, lbtyp2) < 0)
+  if (lstlbl(lbflag) < 0)
     ERROR("Break/continue statement outside of loop\n", 0, EXIT_FAILURE);
   DEBUG("Found Label '%s'\n", tmplbl);
   asmlin("JMP", tmplbl);
@@ -312,8 +312,8 @@ void pslct() {
   expect('(');
   prsxpr(')');            //Parse Expression
   newlbl(endlbl);         //Create New Label
-  pshlbl(LTSLCT,endlbl);  //Push Onto Stack
-  bgnblk('{');           //Require Beginning of Block
+  pshlbl(LTSLCT,endlbl);   //Push Onto Stack
+  bgnblk('{');            //Require Beginning of Block
   strcpy(xstmnt, "CASE"); //Require Next Statement to be CASE
 }
 
@@ -466,9 +466,9 @@ void pstmnt()
   if (wordis("ASM"))
     pasm();
   else if (wordis("BREAK"))
-    pbrcnt(LTEND, LTDWHL);
+    pbrcnt(LFEND);
   else if (wordis("CONTINUE"))
-    pbrcnt(LTLOOP, LTDO);
+    pbrcnt(LFBGN);
   else if (wordis("GOTO"))
     pgoto();
   else if (wordis("INLINE"))