On Inherently Ambiguous E0L Languages

Abstract An E0L system G is called ambiguous if its language contains a word with (at least) two different derivations in G. An E0L language is called inherently E0L-ambiguous if every E0L system generating it is ambiguous. It is demonstrated that there exist inherently ambiguous E0L languages and in particular that the language {amb2n : 1 ⩽ m ⩽ n} ∪ {am2b2n : 1 ⩽ m ⩽ n} is inherently E0L-ambiguous.

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