Remove all non-alpha characters from string

Question

Is there a way how to remove all non-alpha characters (i.e. ,.?! etc) from std::string while not deleting czech symbols like ščéř? I tried using:

std::string FileHandler::removePunctuation(std::string word) {
    for (std::string::iterator i = word.begin(); i != word.end(); i++) {
        if (!isalpha(word.at(i - word.begin()))) {
            word.erase(i);
            i--;
        }
    }
    return word;    
}

but it deletes czech characters.

In the best case, I'd like to use toLowerCase for those symbols too.

Answer 1

You can use std::remove_if along with erase:

#include <cctype>
#include <algorithm>
#include <string>
//...
std::wstring FileHandler::removePunctuation(std::wstring word) 
{
    word.erase(std::remove_if(word.begin(), word.end(), 
                  [](char ch){ return !::iswalnum(ch); }), word.end());
    return word;
}

Answer 2

Here's an idea:

#include <iostream>
#include <cwctype>
// if windows, add this: #include <io.h>
// if windows, add this: #include <fcntl.h>

int main()
{
  // if windows, add this: _setmode( _fileno( stdout ), _O_U16TEXT );
  std::wstring s( L"š1č2é3ř!?" );
  for ( auto c : s )
    if ( std::iswalpha( c ) )
      std::wcout << c;
  return 0;
}