Map/Reduce/Filter

[bearophile]

superdan:
> better said 8x slower and quite a bit dumber too. great deal.

Feel free to suggest how to make parts of the code more enlightened.
Andrei Alexandrescu has lot of more experience than me in C++-like languages, and this is my first lib in in D.

Regarding speed, there are things faster too, like sorting, some string operations, or you can benchmark the levenshtein distance present in the std.algorithm, compared to the version you can find in my libs.

Bye,
bearophile