vec.erase( std::remove_if( vec.begin(), vec.end(), some_condition_functor )  );

 

or:

 

for( std::vector<T>::iterator it = vec.begin(); it != vec.end() )

{

   if( some_condition )  it = vec.erase(it);

   else ++it;

}

 

 

the key here is that erase() returns the next valid iterator. "Stepping back" like that isn't correct - after you call erase on that iterator, it's invalidated. The first method above is usually preferred, the second works but is less efficient.

 

FYI I coded this within the email, so there may be something wrong...

 

Mike

 

---

From: bringiton bringiton [mailto:kneeride@gmail.com]
Sent: Monday, July 10, 2006 11:56 PM
To: boost-users@lists.boost.org
Subject: [Boost-users] erase and iterators

 

is this common practise for using an interator with erase? what i wish to do is interate through each item and delete the item if some condition is true.  when i delete, i need to move back a step so that i dont miss an item.

for (std::vector<int>::iterator it = vect.begin(); it != vect.end(); it++) {
 if ((*it) == 5) { // some condition
  vect.erase(it);
  it--; //  step back
 }
}

or would it be best to use a reverse iterater? (or possible?)

for (std::vector<int>::reverse_iterator it2 = vect.rbegin(); it2 != vect.rend(); it2++) {
 if ((*it) == 5) {
  // i'm not actually sure how to erase with a reverse iterator???
  vect.erase(it2);
 }
}

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