Added multiple return values on functions

c02.c

@@ -45,6 +45,8 @@ void init()
   invasc = FALSE;
   mskasc = FALSE;
   fcase = FALSE;
+  xsnvar[0] = 0;
+  ysnvar[0] = 0;
 }
 
 /* Reads and parses the next Word in Source File */

doc/c02.txt

@@ -1,4 +1,4 @@
-INTRODUCTION
+INTRODUCTION
 
 C02 is a simple C-syntax language designed to generate highly optimized
 code for the 6502 microprocessor. The C02 specification is a highly
@@ -60,7 +60,12 @@ DIRECTIVES
 
 Directives are special instructions to the compiler. They do not directy
 generate compiled code. A directive is denoted by a leading # character. 
-C02 currently supports only one directive.
+
+DEFINE
+
+The #define directive creates a named constant. 
+
+INCLUDE
 
 The #include directive causes the compiler to read and process and external
 file. In most cases, #include directives will be used with libraries of
@@ -110,7 +115,7 @@ A decimal number consists of one to three decimal digits (0 through 9).
 A hexadecimal number consists of a $ followed by two hexadecimal digits 
 (0 through 9 or A through F).
 
-A character literals consists of a single character surrounded by ' symbols.
+A character literal consists of a single character surrounded by ' symbols.
 A ' character may be specified by escaping it with a \. 
 
 Examples:
@@ -478,6 +483,24 @@ Examples:
 Note: An implicit assignment generates an STA opcode with the variable
 as the operand.
 
+PLURAL ASSIGNMENTS
+
+C02 allows a function to return up to three values by specifying multiple
+variables, separated by commas, to the left of the assignment operator (=).
+
+The first and second variables to be assigned may be either simple variables
+or subscripted array elements. The third variable, if used, may only be a 
+simple variable. Registers are not allowed in plural assignments.
+
+Examples:
+  row, col = scnpos();             //Get current screen position
+  cr, mn, mx = cpmnmx(a, b);       //Compare two values, return min and max
+  lwr[i], upr[i] = tolwup(txt[i]); //Convert char to lower and upper case  
+
+Note: When compiled, a plural assignment generates an STX for the third
+assignment (if specified), an STY for the second assignment and an STA for
+the first assignment. 
+
 GOTO STATEMENT
 
 A goto statement unconditionally transfers program execution to the 
@@ -512,9 +535,9 @@ Examples:
 Note: In order to optimize the compiled code, the if and else statements 
 are to 6502 relative branch instructions. This limits the amount of 
 generated code between the if statement and the end of the if/else block
-to slightly less than 127 characters. This should be sufficient in most
-cases, but larger code blocks can be accommodated using function calls or
-goto statements.
+to slightly less than 127 bytes. This should be sufficient in most cases, 
+but larger code blocks can be accommodated using function calls or goto 
+statements.
 
 SELECT, CASE, AND DEFAULT STATEMENTS
 

parse.c

@@ -71,7 +71,7 @@ char getnxt()
 void skpspc() 
 {
   //DEBUG("Skipping Spaces\n", 0);
-  if (isspc()) CCMNT(' ');
+  if (isspc()) CCMNT(' '); //Add only the first space to comments
   while (isspc()) 
     getnxt();
 }
@@ -387,14 +387,6 @@ void prsopr()
   skpspc();
 }
 
-/* Process Array Index */
-void prcidx(char *name, char *index)
-{
-  if (strlen(index)) { 
-      asmlin("LDX", index);
-      strcat(name,",X");
-  }
-}
 
 /* Generate Post-Operation Error */
 void poperr(char* name) 
@@ -407,7 +399,10 @@ void poperr(char* name)
 void prcpst(char* name, char *index) 
 {
   DEBUG("Processing post operation '%c'\n", oper);
-  prcidx(name, index);
+  if (strlen(index)) { 
+      asmlin("LDX", index);
+      strcat(name,",X");
+  }
   switch(oper)
   {    
     case '+': 

parse.h

@@ -4,7 +4,7 @@
 
 #define TF(x) (x) ? TRUE : FALSE;
 
-enum stypes {CONSTANT, VARIABLE, ARRAY, FUNCTION};  //Symbol Types
+enum stypes {CONSTANT, VARIABLE, REGISTER, ARRAY, FUNCTION};  //Symbol Types
 enum etypes {ETDEF, ETMAC};                         //Definition Types
 
 char nxtwrd[LINELEN]; //Next Word (from DEFINE lookup)

stmnt.c

@@ -59,61 +59,115 @@ void prssif(char trmntr) {
   setlbl(tmplbl);         //Emit End of Expression Label
 }
 
+/* Process Array Index */
+void prcidx(int idxtyp, char *name, char *index)
+{
+    if (strlen(index)) { 
+      if (idxtyp == CONSTANT) {
+        strcat(name, "+");
+        strcat(name, index);
+      }
+      else {
+        asmlin("LDX", index);
+        strcat(name,",X");
+      }
+    }
+}
 
 /* Process Assignment */
 void prcasn(char trmntr)
 {
   expect('=');
-  DEBUG("Processing assignment of variable '%s'\n", asnvar);
   if (look('(')) 
     prssif(trmntr); //Parse Shortcut If 
   else
     prsxpr(trmntr); //Parse Expression
+  DEBUG("Processing X assignment variable '%s'\n", xsnvar);
+  if (xsnvar[0]) {
+    asmlin("STX", xsnvar);
+    xsnvar[0] = 0;
+  }
+  DEBUG("Processing Y assignment variable '%s'\n", ysnvar);
+  if (ysnvar[0]) {
+    if (strlen(ysnidx)) 
+      prcidx(ysnivt, ysnvar, ysnidx);
+    asmlin("STY", ysnvar);
+    ysnvar[0] = 0;
+  }
+  DEBUG("Processing assignment variable '%s'\n", asnvar);
   if (strcmp(asnvar, "X")==0)
     asmlin("TAX", "");
   else if (strcmp(asnvar, "Y")==0)
     asmlin("TAY", "");
   else if ((strcmp(asnvar, "A")!=0))
   {
-    if (strlen(asnidx)) { 
-      if (asnivt == CONSTANT) {
-        strcat(asnvar, "+");
-        strcat(asnvar, asnidx);
-      }
-      else {
-        asmlin("LDX", asnidx);
-        strcat(asnvar,",X");
-      }
-    }
+    if (strlen(asnidx)) 
+      prcidx(asnivt, asnvar, asnidx);
     asmlin("STA", asnvar);
   }
 }
 
-/* Process Variable at Beginning of Statement */
+/* Parse and Return Array Index and Type */
+int getidx(char* idx)
+{
+    prsidx();  //Parse Array Index
+    if (valtyp == CONSTANT) 
+	    strncpy(idx, word, VARLEN);
+	else
+    	strncpy(idx, value, VARLEN);
+    DEBUG("Set assigned index to %s\n", asnidx);
+    return valtyp;
+}
+
+/* Process Assignment Variable(s) */
 void prcvar(char trmntr)
 {
   chksym(TRUE, word);
-  strcpy(asnvar, word);  //sav variable to assign to
-  if (valtyp == VARIABLE && look(';')) {
+  strcpy(asnvar, word);  //save variable to assign to
+  asntyp = valtyp; //Set Assigned Varable Type
+  DEBUG("Set STA variable to %s\n", asnvar);
+  if (asntyp == VARIABLE && look(';')) {
     asmlin("STA", asnvar);
     return;
   }
-  if (valtyp == ARRAY) {
-    prsidx();  //Parse Array Index
-    asnivt = valtyp;
-    if (asnivt == CONSTANT) 
-	    strncpy(asnidx, word, VARLEN);
-	else
-    	strncpy(asnidx, value, VARLEN);
+  if (asntyp == ARRAY) {
+    asnivt = getidx(asnidx); //Get Array Index and Type
+    DEBUG("Set STA index to %s\n", asnidx);
+    DEBUG("Set STA index type to %d\n", asnivt);
   }
   else
     asnidx[0] = 0;
   if (ispopr()) {
     if (prspst(trmntr, asnvar, asnidx)) //Parse Post Operator
       expctd("post operator");
+	/*refactor - put a return here and remove followig else*/
   }
-  else
+  else {
+    if (look(',')) {     
+      if (asntyp == REGISTER) {
+        ERROR("Register %s not allowed in plural assignment\n", asnvar, EXIT_FAILURE);
+      }
+      prsvar(FALSE); //get variable name
+      strcpy(ysnvar, word);
+      DEBUG("Set STY variable to %s\n", ysnvar);
+      if (valtyp == ARRAY) {
+        ysnivt = getidx(ysnidx); //Get Array Index and Type
+        DEBUG("Set STY index to %s\n", ysnidx);
+        DEBUG("Set STY index type to %d\n", ysnivt);
+      }
+      else
+        ysnidx[0] = 0;
+      if (look(',')) {
+        prsvar(FALSE); //get variable name
+        strcpy(xsnvar, word);
+        DEBUG("Set STX variable to %s\n", xsnvar);
+        if (valtyp == ARRAY) {
+          ERROR("Array element not allowed in third assignment\n", 0, EXIT_FAILURE);
+	    }
+      }
+    }
     prcasn(trmntr);
+  }
 }
 
 /* Parse 'asm' String Parameter */
@@ -141,7 +195,7 @@ void pasm()
   asmlin(opcode, word);
 }
 
-/* Parse and Compile and Assignment */
+/* Parse and Compile an Assignment */
 void prsasn(char trmntr) 
 {
   getwrd();               //Get Variable to be Assigned

stmnt.h

@@ -3,8 +3,13 @@
  ************************************/
 
 char asnvar[VARLEN+1];      //Assigned Variable Name
+int  asntyp;                //Assigned Variable Type
 char asnidx[VARLEN+1] ;     //Assigned Variable Index
 int  asnivt;                //Assigned Index Variable Type
+char ysnvar[VARLEN+1];      //Assigned Y Variable Name
+char ysnidx[VARLEN+1] ;     //Assigned Variable Index
+int  ysnivt;                //Assigned Index Variable Type
+char xsnvar[VARLEN+1];      //Assigned X Variable Name
 
 char xstmnt[LINELEN];       //Expected Statement
 

vars.c

@@ -36,8 +36,11 @@ int fndvar(char *name)
 void chksym(int alwreg, char *name) 
 {
   if (strlen(name) == 1 && strchr("AXY", name[0])) {
-    if (alwreg) return;
-    else ERROR("Illegal reference to register %s\n", name, EXIT_FAILURE);
+    if (alwreg && valtyp != ARRAY) {
+      valtyp = REGISTER;
+  	  return;
+    }
+    ERROR("Illegal reference to register %s\n", name, EXIT_FAILURE);
   }
   if (!fndvar(name))
     ERROR("Undeclared variable '%s' encountered\n", name, EXIT_FAILURE);