CODEWITHSUNDEEP
c++
Ofer
Ofer

Reputation: 333

Check iterator pointer in c++

I want to know if the following check is necessary:

std::list<int> myList;
.....
for (std::list<int>::iterator itr = myList.begin(); itr != myList.end(); ++itr)
{
   if (itr != NULL) // Is This Check Necessary?
   {
      // DO SOMTHING.
   }    
}

I have seen this check in some places and I'm wondering if that is a necessary check. Maybe this check is necessary if the list is an input to a function?

Thanks, Ofer.

Upvotes: 3

Views: 426

Answers (5)

Rahul Pandey
Rahul Pandey

Reputation: 445

I think there's no way to test if an iterator is uninitialized, But you can initialize iterator to the end() of the container as a default value.

std::list<int>::iterator itr = yourlist.end();
//
if (itr != yourlist.end())
{
    //doSomething
}

Upvotes: 1

premierlee
premierlee

Reputation: 11

It's unnecessary to check.If the myList is empty,then myList.begin() equals to myList.end()

Upvotes: 1

ashgkwd
ashgkwd

Reputation: 195

instead you can use new range based for loops (C++11), so you dont need to deal with iterator checking.

std::list<int> YourList;
for( auto z : YourList ) {
//
std::cout << z;        // z is int
// amazing codes and fun :)
//
}

Upvotes: 1

NPE
NPE

Reputation: 500277

No, it's not necessary. I am not sure it's even valid.

Upvotes: 2

Alon
Alon

Reputation: 1804

No, it is an unnecessary check. You might want to check *itr != nullptr, if the list held some kind of pointers.

Upvotes: 4

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