On representing RE languages by one-sided internal contextual languages

  A. Ehrenfeucht A. Mateescu Gh. Paun G. Rozenberg A. Salomaa

Abstract:

  In this paper we prove that each recursively enumerable language can be written in the form , where is a language generated by a one-sided internal contextual grammar with context-free choice, is a regular language, and is the operation which removes the prefix bounded by the special symbol , which appears exactly once in the strings for which is defined.

 However, the context-free choice sets are always deterministic linear languages of a very simple form. Similar representations can be obtained using one-sided contextual grammars with finite choice and with erased or with erasing contexts.

  Keywords. Formal languages, contextual grammars, recursively enumerable languages.

 Gyenizse Pal 1997. Február 4. Kedd 15:09:10 MET