Ambiguity .

. Ambiguity is problematic because meaning of the programs can be incorrect

. Ambiguity can be handled in several ways

- Enforce associativity and precedence

- Rewrite the grammar (cleanest way)

. There are no general techniques for handling ambiguity

. It is impossible to convert automatically an ambiguous grammar to an unambiguous one

Ambiguity is harmful to the intent of the program. The input might be deciphered in a way which was not really the intention of the programmer, as shown above in the 9-5+2 example. Though there is no general technique to handle ambiguity i.e., it is not possible to develop some feature which automatically identifies and removes ambiguity from any grammar. However, it can be removed, broadly speaking, in the following possible ways:-

1) Rewriting the whole grammar unambiguously.

2) Implementing precedence and associatively rules in the grammar. We shall discuss this technique in the later slides.