S -> S + S / S * S / S / a
2. Unambiguous Grammar :
A context-free grammar is called unambiguous grammar if there exists one and only one derivation tree or parse tree.
X -> AB A -> Aa / a B -> b
Difference between Ambiguous and Unambiguous Grammar :
|S.NO||Ambiguous Grammar||Unambiguous Grammar|
|1.||In ambiguous grammar, the leftmost and rightmost derivations are not same.||In unambiguous grammar, the leftmost and rightmost derivations are same.|
|2.||Amount of non-terminals in ambiguous grammar is less than in unambiguous grammar.||Amount of non-terminals in unambiguous grammar is more than in ambiguous grammar.|
|3.||Length of the parse tree in ambiguous grammar is comparatively short.||Length of the parse tree in unambiguous grammar is comparatively large.|
|4.||Speed of derivation of a tree in ambiguous grammar is faster than that of unambiguous grammar.||Speed of derivation of a tree in unambiguous grammar is slower than that of ambiguous grammar.|
|5.||Ambiguous grammar generates more than one parse tree.||Unambiguous grammar generates only one parse tree.|
|6.||Ambiguous grammar contains ambiguity.||Unambiguous grammar does not contain any ambiguity.|
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