Parse Tree
- Ambiguity: Determined by parse tree(The order of parsing)
Recursive-Descent Parsing
A left-recursive grammar can cause a recursive-descent parser, even one with backtracking, to go into an infinite loop.
So eliminate Left Recursion using left factoring
void A() {
// Choose an A-production, A -> X1 X2 ... Xk
for (i = 1 to k) {
if (Xi is a nonterminal) {
call procedure Xi();
} else if (Xi equals the current input symbol a) {
advance the input to the next symbol;
} else {
/* an error has occurred */
}
}
}
Alternatively (need left factoring)
