Extension methods in c++

Question

I was searching for an implementation of extension methods in c++ and came upon this comp.std.c++ discussion which mentions that polymorphic_map can be used to

Answer 1

Boost Range Library's approach use operator|().

r | filtered(p);

I can write trim for string as follows in the same way, too.

#include 

namespace string_extension {

struct trim_t {
    std::string operator()(const std::string& s) const
    {
        ...
        return s;
    }
};

const trim_t trim = {};

std::string operator|(const std::string& s, trim_t f)
{
    return f(s);
}

} // namespace string_extension

int main()
{
    const std::string s = "  abc  ";

    const std::string result = s | string_extension::trim;
}