What's the best way to trim std::string?

Question

I\'m currently using the following code to right-trim all the std::strings in my programs:

std::string s;
s.erase(s.find_last_not_of(\" \\n\\r\\         


        

Answer 1

Bit late to the party, but never mind. Now C++11 is here, we have lambdas and auto variables. So my version, which also handles all-whitespace and empty strings, is:

#include 
#include 
#include 

inline std::string trim(const std::string &s)
{
   auto wsfront=std::find_if_not(s.begin(),s.end(),[](int c){return std::isspace(c);});
   auto wsback=std::find_if_not(s.rbegin(),s.rend(),[](int c){return std::isspace(c);}).base();
   return (wsback<=wsfront ? std::string() : std::string(wsfront,wsback));
}

We could make a reverse iterator from wsfront and use that as the termination condition in the second find_if_not but that's only useful in the case of an all-whitespace string, and gcc 4.8 at least isn't smart enough to infer the type of the reverse iterator (std::string::const_reverse_iterator) with auto. I don't know how expensive constructing a reverse iterator is, so YMMV here. With this alteration, the code looks like this:

inline std::string trim(const std::string &s)
{
   auto  wsfront=std::find_if_not(s.begin(),s.end(),[](int c){return std::isspace(c);});
   return std::string(wsfront,std::find_if_not(s.rbegin(),std::string::const_reverse_iterator(wsfront),[](int c){return std::isspace(c);}).base());
}