Re: Is this code to find an int in a string okay ?

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Fri, 07 Dec 2007 07:26:26 -0500

Message-ID:

<daniel_t-999C92.07262607122007@earthlink.vsrv-sjc.supernews.net>

In article
<85ec7280-977f-4651-a3f4-2199b4150d10@j44g2000hsj.googlegroups.com>,
Diwa <shettydiwakar@gmail.com> wrote:

Hi Guys,

Is there any better way than below to find an int in a string (e.g.
"30" in "KFStat30A")

// --------------------------------------------------------------
#include <iostream>
#include <sstream>
#include <vector>

using namespace std;

int main()
{
  vector<string> strs ;
  strs.push_back("KFStat30A");
  strs.push_back("KFStat2A");
  strs.push_back("555555");
  strs.push_back("KKKKKK");
  strs.push_back("KKKK555");

  std::string str;

  for (int i=0; i<strs.size(); i++)
  {
     str = "";

     int beg = strs[i].find_first_of("0123456789");

     if (beg != string::npos)
     {
       int end = strs[i].find_first_not_of("0123456789", beg);
       str.assign(strs[i], beg, end-beg);
     }

     cout << strs[i] << " " << str << "\n";
  }
  return 0;
}

// --------------------------------------------------------------

Thanks

What you have is fine, just wrap it into a function and it will look
like this:

string get_int( const string& s )
{
   string result;
   string::size_type front = s.find_first_of( "0123456789" );
   if ( front != string::npos )
   {
      string::size_type back =
            s.find_first_not_of( "0123456789", front );
      result.assign( s, front, back - front );
   }
   return result;
}

.... or you can get creative:

bool is_digit( char c )
{
   return isdigit( c );
}

string get_int( const string& s )
{
   string::const_iterator front = find_if( s.begin(), s.end(),
         &is_digit );
   string::const_iterator back = find_if( front, s.end(),
         compose1( logical_not<bool>(), ptr_fun( &is_digit ) ) );
   return string( front, back );
}

(note: compose1 is part of STL, not part of the standard.)

Once you have the above function, you can operate on your array with
transform.

int main()
{
   vector<string> strs ;
   strs.push_back("KFStat30A");
   strs.push_back("KFStat2A");
   strs.push_back("555555");
   strs.push_back("KKKKKK");
   strs.push_back("KKKK555");

   vector<string> ints;

   transform( strs.begin(), strs.end(),
         back_inserter( ints ), &get_int );

   for ( int i = 0; i < strs.size(); ++i )
      cout << strs[i] << ' ' << ints[i] << '\n';
}