Search (Compare) Functor and std::pair :: STL

Hi.

How do you definte a comparison function for an container of std::pair other than map? I need to search a container of std::pair. For example:

Code:

typedef std::deque<std::pair<std::string, int> > deqStringInt;

deqStringInt example;
example.push_back(std::pair<"December", 21>);

// How do you search an element?

std::find_if(example.begin(), example.end(), std::bind2nd(???

// Functor
class Search : std::binary_function<std::pair<std::string, int>, std::string, bool>
{
public:
   bool operator()(const std::pair<std::string, int> &lp, const std::string &rp)
   {
      return lp->first == rp;
   }
};

Thanks,
Kuphryn

I wrote up a very sloppy solution. I didn't use any functors in mine though. They were given me some beef with v$ so I just did it with a standard compare function. Here is my sample..

Code:

#include <functional>
#include <algorithm>
#include <utility>
#include <iostream>
#include <string>
#include <deque>

// Functor
// Not used in my function..
class Search : public std::binary_function<std::pair<std::string, int>, std::string, bool>
{
  public:
  
     bool operator()(std::pair<std::string, int> &lp, std::string &rp)
     {
        return true;
     }
};

typedef std::deque<std::pair<std::string, int> > deqStringInt;
typedef struct std::pair<std::string, int> PAIR;

// Here is my comparison function
bool simple( std::pair< std::string, int > lp, std::string rp )
{
  return !strcmp( lp.first.c_str(), rp.c_str() );
}

int main( void )
{
  deqStringInt example;
  example.push_back( PAIR("December", 21) );

  // How do you search an element?

  deqStringInt::iterator i = std::find_if( example.begin(), 
                example.end(), 
                std::bind2nd( std::ptr_fun(simple), "December" ) );
                
  if( i != example.end() )
  {
    std::cout << "Found" << std::endl;
  }
  else
  {
    std::cout << "Not Found :(" << std::endl;
  }

  return 0;
}

Tomorrow when I get some sleep I will post up the other version using functors if you'd like.

Nice! Thanks.

I have some questions about your solution. It makes use of something I do not know exists. Anyways, I want to rest too.

Yes, I look forward to possibly a working solution using a functor just to see the use of functor and std:air.

Kuphryn

Update:

Here is the code using the function object:

Code:

#include <functional>
#include <algorithm>
#include <utility>
#include <iostream>
#include <string>
#include <deque>

// Functor
class Search : public std::binary_function<std::pair<std::string, int>, std::string, bool>
{
  public:
  
    bool operator()(std::pair< std::string, int > lp, std::string rp) const
     {
        return !strcmp( lp.first.c_str(), rp.c_str() );
     }
};

typedef std::deque<std::pair<std::string, int> > deqStringInt;
typedef struct std::pair<std::string, int> PAIR;

int main( void )
{
  deqStringInt example;
  example.push_back( PAIR("December", 21) );

  // How do you search an element?

  deqStringInt::iterator i = std::find_if( example.begin(), 
                example.end(), 
                std::bind2nd( Search(), "December" ) );
                
  if( i != example.end() )
  {
    std::cout << "Found" << std::endl;
  }
  else
  {
    std::cout << "Not Found :(" << std::endl;
  }

  return 0;
}

Ugh, I'm such an insomniac. It's 4:30am and I'm messing with the STL. I'm such a loser. Anyways I can't even remember what I changed yours from to get it to work. I know you didn't specify the "public" inheritance in yours. That was a problem. Also the overloaded operator needed to have a const for the data members. There are some subtle things that needed to be done. If you have any questions on what I did or how I arrived at a certain solution PM me or just post it on this thread. Hope it helped you.

Nice!!! Thanks.

Here is the final working solution I implemented using your model.

Code:

class Searc : std::binary_function<pairStringInt, std::string, bool>
   {
   public:
      bool operator()(const pairStringInt &lp, const std::string &rp) const
      {
         return (lp.first == rp);
      }
   };

std::find_if(data.begin(), data.end(), std::bind2nd(Search(), theString))

Kuphryn