Re: [Boost-users] [Regex] Replace algorithm

From: Andrew McDonald (andrew.mcdonald_at_[hidden])
Date: 2006-05-22 23:02:35

Hi, 

The iostreams library has a basic_regex_filter that will do this job.

See 
http://www.boost.org/libs/iostreams/doc/classes/regex_filter.html
or in context
http://www.boost.org/libs/iostreams/doc/index.html
4. Reference -> 4.2 Classes -> basic_regex_filter

The following ctor is the one you probably want
basic_regex_filter( const basic_regex<Ch, Tr, Alloc>& pattern,
                        const formatter& replace,
                        regex_constants::match_flag_type flags = 
                            regex_constants::match_default );

It takes a regex (and regex flags) and for each match calls the formatter function. 
The formatter is a boost::function1 that takes the match_results and is expected to return a string that will be used to replace the match. 

You will probably have to put your src/dst strings into stringstreams to use the filter. 

Note that the library does support a generous additional variety of sinks and sources , files, arrays, zip archives etc.

Please note that I recently found a bug in basic_regex_filter in cases where no match is found. See my earlier posts for a fix. 

regards,

Andrew

> -----Original Message-----
> From: boost-users-bounces_at_[hidden]
> [mailto:boost-users-bounces_at_[hidden]]On Behalf Of Johan Nilsson
> Sent: Monday, 22 May 2006 7:53 PM
> To: boost-users_at_[hidden]
> Subject: [Boost-users] [Regex] Replace algorithm
> 
> 
> Hi,
> 
> I'd like to replace all parts of a string with the results of 
> calling a 
> function, passing the match as a parameter. Some pseudo-code:
> 
> ---
> std::string replacer(smatch& s)
> {
>     return std::getenv(s[1].c_str());
> }
> 
> std::string const input = "This is ${USER} on ${HOST}";
> boost::regex const re("\\$\\{([^\\}]+)\\}");
> std::string result = boost::regex_replace(input, re, 
> boost::bind(&replacer));
> 
> assert("This is Me on MyWorkstation" == result);
> ---
> 
> (I'm sure there are errors above, but I hope you get the 
> general idea).
> 
> Any easy way to do something similar?
> 
> // Johan
> 
> 
> 
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