Can end() be a costly operation for stl containers

Question

On https://doc-snapshots.qt.io/qtcreator-extending/coding-style.html it is recommended to write for loops like the following:

Container::iterator end = large         


        

Answer 1

This is less about end being costly and more about the ability of a compiler to see that end will not change through a side effect in the loop body (that it is a loop invariant).

The complexity of end is required to be constant by the standard. See table 96 in N3337 in 23.2.1.

Using standard library algorithms circumvents the whole dilemma nicely.