C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

88. Prefer function objects over functions as algorithm and comparer arguments

Summary

Objects plug in better than functions: Prefer passing function objects, not functions, to algorithms. Comparers for associative containers must be function objects. Function objects are adaptable and, counterintuitively, they typically produce faster code than functions.

Discussion

First, function objects are easy to make adaptable, and always should be (see Item 89). Even if you already have a function, sometimes you have to wrap it in ptr_fun or mem_fun anyway to add adaptability. For example, you have to do this in order to build up more complex expressions using binders (see also Item 84):

The usual workaround is to insert ptr_fun (or, for a member ...