# Filter::cpp - phpMan

## NAME
    [Filter::cpp] - cpp source filter

## SYNOPSIS
        use [Filter::cpp] ;

## DESCRIPTION
    This source filter pipes the current source file through the C
    pre-processor (cpp) if it is available.

    As with all source filters its scope is limited to the current source
    file only. Every file you want to be processed by the filter must have a

        use [Filter::cpp] ;

    near the top.

    Here is an example script which uses the filter:

        use [Filter::cpp] ;

        #define FRED 1
        $a = 2 + FRED ;
        print "a = $a\n" ;
        #ifdef FRED
        print "Hello FRED\n" ;
        #else
        print "Where is FRED\n" ;
        #endif

    And here is what it will output:

        a = 3
        Hello FRED

    This example below, provided by Michael G Schwern, shows a clever way to
    get Perl to use a C pre-processor macro when the [Filter::cpp] module is
    available, or to use a Perl sub when it is not.

        # use [Filter::cpp] if we can.
        BEGIN { eval 'use [Filter::cpp]' }

        sub PRINT {
            my($string) = shift;

        #define PRINT($string) \
            (print $string."\n")
        }

        PRINT("Mu");

    Look at Michael's [Tie::VecArray] module for a practical use.

## AUTHOR
    Paul Marquess

## DATE
    11th December 1995.