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Commented code in expr.c

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This commit is contained in:
Curtis F Kaylor 2018-07-21 19:15:07 -04:00
parent 0082eb3096
commit f179acceb1
1 changed files with 33 additions and 24 deletions
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57
src/expr.c
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@ -17,19 +17,22 @@
/* Push Term and Operator onto Stack */
void pshtrm(void) {
if (trmidx >= MAXTRM) ERROR("Maximum Function Call/Array Index Depth Exceeded", 0, EXIT_FAILURE)
oprstk[trmidx] = oper;
strcpy(trmstk[trmidx++], term);
oprstk[trmidx] = oper; //Put Current Operator on Stack
strcpy(trmstk[], term); //Put Current Term on Stack
trmidx++; //Increment Stack Pointer
}
/* Pop Term and Operator off Stack */
void poptrm(void) {
strcpy(term, trmstk[--trmidx]);
oper = oprstk[trmidx];
trmidx--; //Decrement Stack Pointer
strcpy(term, trmstk[trmidx]); //Restore Current Term from Stack
oper = oprstk[trmidx]; //Restore Current Operator from Stack
}
/* Parse value (literal or identifier) *
/* Parse value (literal or identifier) *
* Args: alwreg - allow registers *
* Sets: value - the value (as a string) *
* valtyp - value type */
* valtyp - value type */
void prsval(int alwreg) {
DEBUG("Parsing value\n", 0)
skpspc();
@ -46,17 +49,23 @@ void prcmns(void) {
asmlin("LDA", "#$00"); //Handle Unary Minus
}
/* Parse array index *
* Sets: value - array index or *
* "" if no index defined */
/* Parse array index *
* Args: clbrkt - require closing bracket *
* Sets: value - array index or *
* "" if no index defined */
void prsidx(int clbrkt) {
expect('[');
prsval(TRUE);
prsval(TRUE); //Parse Value, Allowing Registers
DEBUG("Parsed array index '%s'\n", value)
if (clbrkt) expect(']');
}
/* Process Simple Array Index */
/* Process Simple Array Index *
* Uses: term - array variable name *
* valtyp - array index value type *
* value - array index as string *
* word - array index raw string *
* Sets: term - modified variable name */
void prcsix(void) {
if (valtyp == LITERAL) {
strcat(term, "+");
@ -104,7 +113,7 @@ void chkidx(void) {
* Sets: term - the term (as a string) */
void prstrm(void) {
DEBUG("Parsing term\n", 0)
prsval(FALSE);
prsval(FALSE); //Parse Term - Disallow Registers
if (valtyp == FUNCTION) ERROR("Function call only allowed in first term\n", 0, EXIT_FAILURE)
strcpy(term, value);
DEBUG("Parsed term %s\n", term)
@ -192,7 +201,7 @@ void prcftm(void) {
/* Parse first term of expession *
* First term can include function calls */
void prsftm(void) {
prsval(TRUE);
prsval(TRUE); //Parse Value, Allowing Registers
prcftm();
}
@ -201,12 +210,12 @@ void prsftm(void) {
void prcopr(void) {
DEBUG("Processing operator '%c'\n", oper)
switch(oper) {
case '+': asmlin("CLC", ""); asmlin("ADC", term); break;
case '-': asmlin("SEC", ""); asmlin("SBC", term); break;
case '&': asmlin("AND", term); break;
case '+': asmlin("CLC", ""); asmlin("ADC", term); break; //Addition
case '-': asmlin("SEC", ""); asmlin("SBC", term); break; //Subtraction
case '&': asmlin("AND", term); break; //Bitwise AND
case '!': //For systems that don't have pipe in character set
case '|': asmlin("ORA", term); break;
case '^': asmlin("EOR", term); break;
case '|': asmlin("ORA", term); break; //Bitwise OR
case '^': asmlin("EOR", term); break; //Bitwise XOR
default: ERROR("Unrecognized operator '%c'\n", oper, EXIT_FAILURE)
}
oper = 0;
@ -216,11 +225,11 @@ void prcopr(void) {
void prsrxp(char trmntr) {
skpspc();
while (isoper()) {
trmcnt++;
trmcnt++; //Increment Expression Depth
prsopr(); //Parse Operator
prstrm(); //Parse Term
prcopr(); //Process Operator
trmcnt--;
trmcnt--; //Decrement Expression Depth
}
expect(trmntr);
}
@ -229,8 +238,8 @@ void prsrxp(char trmntr) {
void prsxpr(char trmntr) {
DEBUG("Parsing expression\n", 0)
skpspc();
trmcnt = 0;
if (match('-')) prcmns();
else prsftm(); //Parse First Term
prsrxp(trmntr);
trmcnt = 0; //Initialize Expression Depth
if (match('-')) prcmns(); //Process Unary Minus
else prsftm(); //Parse First Term
prsrxp(trmntr); //Parse Remainder of Express
}