And why if you want transform_if you'll really appreciate ranges:

std::transform, a central algorithm

by Jonathan Boccara

From the article:

The concept of std::tranform is so useful that there is a name for it, coming from functional programming: map (unrelated to std::map). In fact, we can see it the other way round: the STL takes its root in functional programming, so it is only normal that a central concept in functonal programming gets a central role in the STL...