Greibach normal form

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Greibach normal form A restricted type of context-free grammar, namely one in which all productions have the form AbC1Cn

i.e. each right-hand side consists of a terminal followed by (zero or more) nonterminals. Any context-free language is generated by such a grammar, except that derivation of the empty string, Λ, requires the additional production S → Λ

One significance of this form is that it makes clear the existence of an equivalent pushdown automaton: on reading b the PDA can pop A from the stack and push C1Cn.

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Greibach normal form

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