string find_first_of fails

[stober]

why does this fail (VC6 on W2K)

#include <string>

int main()
{
   string spath = "\\windows\\something";

   if(spath.find_first_of("*?") >= 0)
   {
       // this is always true 
       // remove the wild cards
   }
}

But this works ok:

#include <string>
int main()
{
   string spath = "\\windows\\something";
   int pos = spath.find_first_of("*?");
   if(pos >= 0)
   {
       // remove the wild cards
   }
}

[jfaust]

find_first_of returns type of size_type, which looks like it's unsigned int. Of course it's always >= 0. In the second example, you are casting it to an int.

Jeff

[Philip Nicoletti]

When using std::string search/find functions, if not found
a special value is returned ... string::npos

So your check should look like this :

#include <string>
#include <iostream>

int main()
{
    std::string spath = "\\windows\\something";

    if(spath.find_first_of("*?") != std::string::npos)
    {
       std::cout << "found wildcard" << std::endl;
    }

    // edit adding further clarification ...


   int pos1 = spath.find_first_of("?*");
   cout << "as an int : " << pos1 << endl; 

   string::size_type pos2 = spath.find_first_of("?*");
   cout << "as a string::size_type : " << pos2 << endl; 

   cout << "string::npos = " << string::npos << endl;


   return 0;
}