Formal Languages and Translators: Difference between revisions
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Revision as of 19:46, 13 June 2018
Internal
Formal Grammars
A set of production rules that describe all possible strings in a given formal language. The rules describe how to form strings from the language's alphabet that are valid according to the language syntax. The grammar does not describe the meaning of strings, or what can be done with them in whatever context, only their form.
Context-Free Grammar
A context-free grammar is a grammar in which the left-hand side of each production rule consists of only a single nonterminal symbol. A popular notation for context-free grammar is Backus-Naur (BNF).
Backus-Naur Form BNF
Backus-Naur form is notation technique for context-free grammars that is used to describe the syntax of languages used in computing.
A BNF specification is a set of derivation rules, written as:
<symbol> ::= expression
where <symbol> is a nonterminal, and expression consists of one or more sequence of symbols. The expression may contain vertical bars '|' indicating a choice. Symbols that. never appear on the left side are terminals. The ::= means that the symbol on the left must be replaced with the expression on the right.