Lex Tutorial

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Phases of Compilation

Lex

  • Lex is a program that generates lexical analyzer. It is used with YACC parser generator.
  • The lexical analyzer is a program that transforms an input stream into a sequence of tokens.
  • It reads the input stream and produces the source code as output through implementing the lexical analyzer in the C program.

The function of Lex is as follows:

  • Firstly lexical analyzer creates a program lex.1 in the Lex language. Then Lex compiler runs the lex.1 program and produces a C program lex.yy.c.
  • Finally C compiler runs the lex.yy.c program and produces an object program a.out.
  • a.out is lexical analyzer that transforms an input stream into a sequence of tokens.
Running Lex Programs