lex code for prime number

Lex is a computer program that generates lexical analyzers ("scanners" or "lexers").Lex is commonly used with the yacc parser generator. Lex, originally written by Mike Lesk and Eric Schmidt and described in 1975,is the standard lexical analyzer generator on many Unix systems, and an equivalent tool is specified as part of the POSIX standard.[citation needed]Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language.