Re: [Boost-Users] Regex recommended usage?

From: Duane Murphy (duanemurphy_at_[hidden])
Date: 2002-07-09 10:19:20

--- At Tue, 9 Jul 2002 11:11:50 +0200, Daniel Frey wrote:

>Hi,
>
>I have a container (map) with identifiers and value and would like to
>replace variables in a string. The function to perform the replacement I
>wrote needs a const_cast, which makes me a bit nervous. Is this
>necessary? Is there a better way to implement it?
>
>Here's the code:
>
>// The global variable container;
>map< string, string > variables;
>
>const string resolv_variables( string s )
>{
>    // Variables (...${identifier}...) are matched by:
>    static const boost::regex find( "(?:^|.*[^\\\\])(\\$\\{"   // start
>                                    "([a-zA-Z_][a-zA-Z0-9_]*)" // identifier
>                                    "\\}).*" );                // end
>
>    boost::smatch what;
>    while( boost::regex_match( s, what, find ) ) {
>        const string::iterator begin =
>            const_cast< string::iterator >( what[ 1 ].first );
>
>        const string::iterator end =
>            const_cast< string::iterator >( what[ 1 ].second );
>
>        const string identifier = what[ 2 ];
>
>        s = s.replace( begin, end, variables[ identifier ] );
>    }
>
>    return s;
>}

This is shooting from the hip, but it seems like this might need to be:

>        const string::iterator begin =
>            const_cast< string::iterator >( what[ 1 ].first );

string::const_iterator begin = what[ 1 ].first;

I havent looked at regex to know if this is right. Its just a guess from
knowing how iterators work. ( const iterator != const_iterator )

 ...Duane

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