erase() after performing remove_if()

Question

I\'ve created a function to run through a vector of strings and remove any strings of length 3 or less. This is a lesson in using the STL Algorithm library.

I\'m ha

Answer 1

It is easiest to understand this if you seperate the statements:

auto iter(remove_if(myVector.begin(), myVector.end(), StringLengthTest));
myVector.erase(iter);

These 2 lines do the same as your single line. And it should be clear now what the "bug" is. remove_if, works first. It iterates over the whole vector and moves all "selected" entries "to the end" (better said: it moves the non selected entries to the front). After it has run it returns an iterator to the "last" position of the left over entries, something like:

this
test
vector
test <- iterator points here
vector

Then you run erase with a single iterator. That means you erase a single element pointed at - so you erase the "test" element. - What is left over is what you are seeing.

To fix it simply erase from the vector returned by remove_if to the end().:

myVector.erase(remove_if(myVector.begin(), myVector.end(), StringLengthTest), myVector.end()); //erase anything in vector with length <= 3

Answer 2

You should be using the two parameter form of erase:

myVector.erase(remove_if(myVector.begin(), myVector.end(), StringLengthTest),
               myVector.end());