What makes STL fast? [closed]

Question

If one implements an array class the way it is commonly implemented, its performance is slower compared to its STL equivalent like a vector. So what makes STL containers/algorithms fast?

Answer 1

STL algorithms like for_each take function objects that can be easily inlined. C, on the other hand, uses function pointers which are much more difficult for the compiler to optimize.

This makes a big difference in some algorithms like sorting in which the comparer function must be called many times.

Wikipedia has some more information in case you are interested.

EDIT:

As for the STL's vector class, I don't think it's necessarily faster that what you could find in, say, glibc.

Answer 2

Most people's array classes increase the size by a constant increment rather than a constant factor (as the standard library requires). This means inserting an element takes roughly linear time rather than the amortized constant time for the standard library.