//Parse and translate a Math Expression
void expression(){
if (isAddop(look)) {
emitln("xor\t%eax,%eax"); //unary - or + so first operand is zero
}else{
term();
}
while (isAddop(look)) {
emitln("push\t%eax"); //push eax to top of stack
switch (look) {
case '+':
add();
break;
case '-':
substract();
break;
default:
expected("Addop");
break;
}
}
}
int expression() {
int retVal;
if (isAddop(look)) {
retVal = 0;
}
else {
retVal = term();
}
while (isAddop(look)) {
switch (look) {
case '+':
match('+');
retVal += term();
break;
case '-':
match('-');
retVal -= term();
break;
}
}
return retVal;
}
/* EBNF: additive-expression -> term {addop term} */
static TreeNode * additive_expression (void)
{ TreeNode * t = term();
TreeNode * newNode;
while (token == COMMENT) unexpectedTokenHandling();
/* {addop term} */
while (isAddop(token))
{ newNode = newExpNode (OpK);
if (newNode != NULL)
{ newNode->child[0] = t;
newNode->attr.op = token;
t = newNode;
}
match (token); // match addop
if (t != NULL)
t->child[1] = term();
}
return t;
}
static int isOp (TokenType token)
{ if (isRelop(token)||isAddop(token)||isMulop(token))
return TRUE;
else
return FALSE;
}
