C++ iterator question

[d4u7211]

using the following code:

list<string>::iterator iter;
for (iter=names.begin(); iter!=names.end(); iter++) {
names.erase(iter);
}

we are supposed to assume that the program compiles but does not execute properly (logical error causing a CRASH). The list holds 20 names. What is wrong, I don't see anything wrong with it (but I'm sort of new on the whole pointer thing)?

names.end() points to the imaginary space after the last element in the list. begin() points at the first element of the list.

my two guesses is that either:
iter!=names.end() should be something else, or
names.erase(iter) should be names.erase(*iter);

[FissionMailed1]

Re: C++ iterator question

When you erase from std::list, you delete the reference to the iterator. In other words, after it is deleted, "iter++" has no idea where it needs to go next, because you just deleted "iter". You need to save where the iterator is in the list, so you just use the return value from erase(). All you would have to do to fix that code segment is change "names.erase(iter)" to "iter = names.erase(iter)" so you don't lose your position when you are traversing the list.

[d4u7211]

Re: C++ iterator question

When you erase from std::list, you delete the reference to the iterator. In other words, after it is deleted, "iter++" has no idea where it needs to go next, because you just deleted "iter". You need to save where the iterator is in the list, so you just use the return value from erase(). All you would have to do to fix that code segment is change "names.erase(iter)" to "iter = names.erase(iter)" so you don't lose your position when you are traversing the list.

Ah, thank you very much :) i didn't really understand how .erase() worked (my book does not go into detail on it it seems...) - found http://www.cplusplus.com/reference/list/list/erase/ after your suggestion to further understand how it worked. I didn't know list::erase had a return value. (nor did i know if sending in the pointer to erase() would automatically dereference the variable or not, etc., if that was how it worked)