34.5. Functors and Ranges: Coda

This chapter has been taking a somewhat meandering tour of what is at best a mild, often unnoticed, gripe with having to make too many keystrokes, but at worst can be a serious detriment to maintainability.

We've looked at the trade-offs between unrolled loops and functors, and some of the imperfections in the language in terms of the difficulties of using local functors.

We've also seen how we can maximize the generality of functors, by making them compatible with a wider variety of types, via character type parameterizations, type tunneling, and adaptor argument type parameterization. The combination of these techniques represents a substantial resolution of the issues raised in the early part of the chapter.

Last, we looked at the Range concept. Not only do ranges provide a nice syntactic convenience, but they also facilitate the unified manipulation of iterator-bound ranges and what we might call purely logical ranges. Furthermore, the application of range filters, to both kinds of ranges, represents a powerful but simple-to-use mechanism for criteria-driven manipulation of ranges.

Update: The latest work on Ranges has incorporated callback enumeration APIs (in the form of the Indirect Range)—something that cannot be handled by STL iterators. See http://www.rangelib.org/ for the latest details.