Re: How to pass the field name of a struct as a parameter?

Markus Schoder wrote:


Try this (I didn't test it, but it compiles :-) ). I think it should
work with VC++ 6, and it works with keys of different types and
different names:

 #include <vector>
 #include <cassert>

 using namespace std;

 template<class Iterator, typename key_type, typename T>
 Iterator minfield(
   Iterator start,
   const Iterator &end,
   key_type T::*p)
 {
   key_type acc = (*start).*p;
   Iterator min_i(start);
   ++start;
   while(start != end)
   {
     const key_type &r = (*start).*p;
     if(r < acc)
     {
       acc = r;
       min_i = start;
     }
     ++start;
   }
   return min_i;
 }

 struct S1
 {
   typedef int key_type;
   key_type key1;
   S1( key_type key ) : key1(key) {}
 };

 struct S2
 {
   typedef double key_type;
   key_type key2;
   S2( key_type key ) : key2(key) {}
 };

 int main()
 {
   std::vector<S1> v1;
   v1.push_back( S1(1) );
   v1.push_back( S1(5) );
   v1.push_back( S1(-10) );
   v1.push_back( S1(3) );

   vector<S1>::const_iterator m1 = minfield(
     v1.begin(), v1.end(), &S1::key1 );
   assert( m1->key1 == -10 );

   std::vector<S2> v2;
   v2.push_back( S2(1.1) );
   v2.push_back( S2(5.1) );
   v2.push_back( S2(-1.1) );
   v2.push_back( S2(3.1) );

   vector<S2>::const_iterator m2 = minfield(
     v2.begin(), v2.end(), &S2::key2 );
   assert( m2->key2 == -1.1 );

   return 0;
 }

Cheers! --M