Re: iterator error

"Jim Langston" <>
Thu, 5 Apr 2007 21:14:23 -0700
"??????????" <> wrote in message

windows xp, visual studio 2005
#include <iostream>
#include <map>
using namespace std;

int main()
map<int, int>::iterator it = 0;
if( it != 0 ) //break point,
this is an run time error?
why it can be assign "0", but can't compare with "0"?

Read the other's comments. You are trying to compare an iterator and an
integer. On some (most?) implementations it = 0 would probably be invalid
also. The correct usage is to initialize them with .begin() or .rbegin() or
some iterator value. For example:

int main()
   std::map<int, int> MyMap;
   std::map<int, int>::iterator it = MyMap.begin();
   // code

persontally, I normally use iterators mostly in for loops to iterate through
a container (vector or map) or to get a pointer to a newly inserted member.
Such as:

typedef std::map<int, int> IntMap;
IntMap MyMap;
// fill MyMap
for ( IntMap::iterator it = MyMap.begin(); it != MyMap.end(); ++it )
   std::cout << it->first << "-" << it->second << "\n";

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