actions before parsing rules in lex n yacc

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11-26-2008

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actions before parsing rules in lex n yacc

Hi ,

We have developed a grammer for our domain language using lex n yacc.
I want to know is there any pre defined lex-yacc function which gets call before executing any rule (or rules).
Oue requirement is, before processing any rule ,we want to perform some specific actions ?
is there any pre defined lex-yacc function which get call before processing rules?

In case of ANTLR (Another Tool for Language Recognition), we can specify actions before processing rule using a block "@init" . Is there anything like "@init" in lex n yacc ?

Regards,
Suprit

supritjain

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lex

lex(1)							      General Commands Manual							    lex(1)

Name
       lex - generate lexical analyzer

Syntax
       lex [-tvfn] file...

Description
       The  command  generates	programs  to be used in simple lexical analysis of text.  The input files (standard input default) contain regular
       expressions to be searched for, and actions written in C to be executed when expressions are found.

       A C source program, 'lex.yy.c', is generated.  It is compiled using the following command line:
       cc lex.yy.c -ll
       This program copies unrecognized portions of the input to the output, and executes the associated C action for each regular expression that
       is recognized.

Options
       -f   Runs a faster compilation (does not pack resulting tables).  This is limited to small programs.

       -n   Prints no summary information (default option).

       -t   Writes to standard output instead of to file

       -v   Prints one-line summary of generated statistics.

Examples
       In the following example, the command
       lex lexcommands
       draws instructions from the file lexcommands, and places the output in lex.yy.c.  The command
       %%
       [A-Z]	 putchar(yytext[0]+'a'-'A');
       [ ]+$
       [ ]+ putchar(' ');

       is  an example of a program that would be put into a command file.  This program converts upper case to lower, removes blanks at the end of
       lines, and replaces multiple blanks by single blanks.

See Also
       sed(1), yacc(1)
       "LEX - Lexical Analyzer Generator", Supplementary Documents, Volume 2: Programmer

																	    lex(1)

Programming