BSU bulletin. Mathematics, Informatics
HOMOMORPHISM OF EQUIVALENT TRANSFORMATIONS OF GRAMMARS IN PARSER GENERATION // BSU bulletin. Mathematics, Informatics. - 2019. №2. . - С. 44-60.
HOMOMORPHISM OF EQUIVALENT TRANSFORMATIONS OF GRAMMARS IN PARSER GENERATION
When constructing a translator, as a rule, it is necessary to apply the equivalent transformations of grammar of the implemented language, which convert the syn- tactic specification of the language into a form that allows for automatic or manual implementation of the source language, and solves the problem of constraint satis- faction of the chosen parsing technique. These problems arise both because of the variety of ways of defining the implemented languages, and because of the lan- guage ambiguity or nondeterminism of the recognizing automaton. Each transfor- mation performed on translational CF-grammars can be defined as a likelihood ratio (homomorphism), determined on classes of grammars. Such relations preserve the semantic meaning of grammatical structures in equivalent syntax transformations, since the ultimate purpose of translation is to obtain a sequence of actions pre- scribed by the computing environment.
The article presents a brief overview of various types of likelihood ratio over grammars used in constructing translators since the 1970s.
A flow chart for LL parsing with use of syntactic graph scheme (SGS) is presented. We have given a formal notion of a route (path) in the SGS and an example of the automatic CFR-grammar transformation of CIAO formal language in SynGT (Syntax Graph Transformations) system of equivalent transformations.
equivalent transformations of grammars; likelihood ratio; cover homo- morphism; CF-grammar in a regular form (CFR-grammar); syntactic graph scheme (flow-chart); grammar regularization.
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