best tool in Boost for (massive) string replacement?
With all the tools available in Boost and coming from a different
backgroup is hard for me to choose what is the best tool in Boost to
do a massive string replacement.
The problem I have is the following, I have a map of replaced and
replacing strings
std::map
Am 24.09.2010 00:11, schrieb alfC:
Spirit should do that quite fast, but of course it's difficult to know which one is fastest. Spirit-Code can be optimized during compilation, so make sure to use a static const map, if possible. Regards, michi7x7
alfC
Depending on where you want to spend your runtime (setup cost v. per-line cost), and how much memory you have available... It might be faster to build a single regex that has all your targets as alternates, then use the match data to map to the correct replacement. In Perl, it'd go something like this: # establish mapping from target to replacement. my %reps = ( '\alpha' => 'a', '\beta' => 'b', '\gamma' => 'g' ); # create a regular expression consisting of all targets, using # alternation: my $re = join '|', map { quotemeta $_ } keys %reps; # now loop over the data: while ( my $line = <STDIN> ) { # every time the regex matches, capture what matched into $1 and # then replace it by looking up the target in the %reps map. $line =~ s/($re)/$reps{$1}/g; print $line; } A rough translation into Boost can be found here: http://scrye.com/~tkil/boost/regex/multi-rep.cpp It will still fail if any of your target strings contain "\E" literally in them; I couldn't find any obvious "quotemeta" replacement in boost::regex. There are ways to get fancier with it, but I started running into version incompatibilities. In particular, current implementations of boost::regex allow the replacement formatter to be any arbitrary functor, and my subroutine 'replace' turns into this: struct find_replacement { const ssmap & dict_; find_replacement( const ssmap & dict ) : dict_( dict ) {} const std::string & operator()( const std::string s ) const { return dict_.at( s ); } }; const std::string replace( const std::string & input, const ssmap & dict, const boost::regex & re ) { find_replacement fr( dict ); return boost::regex_replace( input, re, fr ); } Happy hacking, t.
On 9/23/2010 6:11 PM, alfC wrote:
None of the above. Use Boost.Xpressive. The complete solution is below:
#include <map>
#include <string>
#include <iostream>
#include
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michi7x7