#include <functional>
#include <iterator>
#include <iostream>
#include <boost/lexical_cast.hpp>
#include <boost/regex.hpp>
///In_regex is a predicate that determines if a character
///matches a regular expression.
///From http://www.richelbilderbeek.nl/CppIn_regex.htm
struct In_regex : public std::unary_function<char, bool>
{
In_regex(const std::string& regex)
: m_regex(regex)
{
}
bool operator()(const char c) const
{
return boost::regex_match(
boost::lexical_cast<std::string>(c),
m_regex);
}
const boost::regex m_regex;
};
//Copy_if was dropped from the standard library by accident.
template<typename In, typename Out, typename Pred>
Out Copy_if(In first, In last, Out res, Pred Pr)
{
while (first != last)
{
if (Pr(*first))
*res++ = *first;
++first;
}
return res;
}
int main()
{
std::string s = "abcdefghijklmnopqrstuvwxyz";
Copy_if(s.begin(),s.end(),
std::ostream_iterator<char>(std::cout,""),
In_regex("a|c|e"));
std::cout << '\n';
Copy_if(s.begin(),s.end(),
std::ostream_iterator<char>(std::cout,""),
In_regex("[f-p]"));
std::cout << '\n';
}
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