| PackageDescription | A fast lexical analyzer generator.
Flex is a tool for generating scanners: programs which recognized lexical
patterns in text. It reads the given input files for a description of a
scanner to generate. The description is in the form of pairs of regular
expressions and C code, called rules. Flex generates as output a C source
file, lex.yy.c, which defines a routine yylex(). This file is compiled
and linked with the -lfl library to produce an executable. When the
executable is run, it analyzes its input for occurrences of the regular
expressions. Whenever it finds one, it executes the corresponding C code.
.
The behaviour of Flex has undergone a major change since version
2.5.4a. Flex scanners are now reentrant, and it is now possible to
have multiple scanners in the same program with differing sets of
defaults, and the scanners play nicer with modern C and C++
compilers. The Flip side is that Flex no longer conforms to the POSIX
lex behaviour, and the scanners require conforming implementations
when flex is used in ANSI C mode. The package flex-old provides the
older behaviour. |