plex-3.0.0 - Online in the Cloud

PROGRAM:

NAME

plex - The Pascal Lex lexical analyzer generator.

USAGE

lex [options] lex-file[.l] [output-file[.pas]]

OPTIONS

-v Verbose: plex generates a readable description of the generated lexical analyzer,
written to lex-file with new extension .lst

-o Optimize: plex optimizes DFA tables to produce a minimal DFA.

DESCRIPTION

plex is a program generator that is used to generate the Turbo Pascal source code for a
lexical analyzer subroutine from the specification of an input language by a regular
expression grammar.

plex parses the source grammar contained in lex-file (with default suffix .l) and writes
the constructed lexical analyzer subroutine to the specified output-file (with default
suffix .pas); if no output file is specified, output goes to lex-file with new suffix
.pas. If any errors are found during compilation, error messages are written to the list
file (lex-file with new suffix .lst).

The generated output file contains a lexical analyzer routine, yylex, implemented as:

function yylex : Integer;

This routine has to be called by your main program to execute the lexical analyzer. The
return value of the yylex routine usually denotes the number of a token recognized by the
lexical analyzer (see the return routine in the LexLib unit). At end-of-file the yylex
routine normally returns 0.

The code template for the yylex routine may be found in the yylex.cod file. This file is
needed by TP Lex when it constructs the output file. It must be present either in the
current directory or in the directory from which TP Lex was executed (TP Lex searches
these directories in the indicated order). (NB: For the Linux/Free Pascal version, the
code template is searched in some directory defined at compile-time instead of the
execution path, usually /usr/lib/fpc/lexyacc.)

The TP Lex library (LexLib) unit is required by programs using Lex-generated lexical
analyzers; you will therefore have to put an appropriate uses clause into your program or
unit that contains the lexical analyzer routine. The LexLib unit also provides various
useful utility routines; see the file lexlib.pas for further information.

MORE INFORMATION

For more information, see the documentation that comes with plex and yacc.

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