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Asked: 2026-05-11T03:29:18+00:00

I was playing around with Boost.Regex to parse strings for words and numbers. This

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I was playing around with Boost.Regex to parse strings for words and numbers. This is what I have so far:

#include <iostream> #include <string> #include <boost/foreach.hpp> #include <boost/regex.hpp> #include <boost/range.hpp>  using namespace std; using namespace boost;  int main() {     regex re     (         '('             '([a-z]+)|'             '(-?[0-9]+(\\.[0-9]+)?)'         ')'     );      string s = 'here is a\t list of Words. and some 1239.32 numbers to 3323 parse.';     sregex_iterator m1(s.begin(), s.end(), re), m2;      BOOST_FOREACH (const match_results<string::const_iterator>& what, make_iterator_range(m1, m2)) {         cout << ':' << what[1].str() << ':' << what.position(1) << ':' << what.length(1) << endl;     }      return 0; }

Is there a way to tell regex to parse from a stream rather than a string? It seems like it should be possible to use any iterator.

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1 Answer

  1. Boost.IOStreams has a regex_filter allowing one to perform the equivalent of a regex_replace on a stream. However, looking at the implementation, it seems to ‘cheat’ in that it simply loads the whole stream into a buffer and then calls Boost.Regex on that buffer.

    Making a regex search on a stream’s contents without having to entirely load it in memory can be done with the ‘partial match‘ support of Boost.Regex. Look at the example at the end of the page.

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