An easy proof of Greibach normal form
Information and Control
Formal languages
Grail: a C++ library for automata and expressions
Journal of Symbolic Computation - Special issue on “algorithms: implementation, libraries and use”
Regular expression for a language without empty word
Theoretical Computer Science
A New Normal-Form Theorem for Context-Free Phrase Structure Grammars
Journal of the ACM (JACM)
A List Structure Form of Grammars for Syntactic Analysis
ACM Computing Surveys (CSUR)
Theory of Computation: A Primer
Theory of Computation: A Primer
Introduction to Formal Language Theory
Introduction to Formal Language Theory
The Theory of Parsing, Translation, and Compiling
The Theory of Parsing, Translation, and Compiling
PODP '96 Proceedings of the Third International Workshop on Principles of Document Processing
Greibach Normal Form Transformation, Revisited
STACS '97 Proceedings of the 14th Annual Symposium on Theoretical Aspects of Computer Science
On the complexity of grammar and language problems.
On the complexity of grammar and language problems.
Grammar transformations based on regular decompositions of context-free derivations.
Grammar transformations based on regular decompositions of context-free derivations.
On the equivalence, containment, and covering problems for the regular and context-free languages
Journal of Computer and System Sciences
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We investigate the complexity of a variety of normal-form transformations for extended context-free grammars, where by extended we mean that the set of right-hand sides for each nonterminal in such a grammar is a regular set. The study is motivated by the implementation project GraMa which will provide a C++ toolkit for the symbolic manipulation of context-free objects just as Grail does for regular objects. The results are that all transformations of interest take time linear in the size of the given grammar giving resulting grammars that are larger by a constant factor than the original grammar. Our results generalize known bounds for context-free grammars but do so in nontrivial ways. Specifically, we introduce a new representation scheme for extended context-free grammars (the symbol-threaded expression forest), a new normal form for these grammars (dot normal form) and new regular expression algorithms.