map! filter! and range algorithm

[bearophile]

H. S. Teoh:

> A range is an abstraction akin to C++'s iterators (except 
> better, IMO).

Stepanov himself has commented very briefly about Alexandrescu/D 
Ranges in one of his video lessons. I have not fully understood 
what Stepanov has said with those few words spoken in a not so 
good English (not because of language, but because Stepanov is 
still out of my league, he's a Teacher) but I think he has 
dismissed the Ranges. A bit like a chemist would dismiss a person 
that says that molecules are more important than atoms and only 
molecules should be used.

I think he has said that atoms are there (in a kind of 
mathematical Platonism), even if you try to ignore them, they are 
more fundamental. So Ranges are a little abstraction over 
C++-style iterators. They are maybe more handy, safer, they allow 
you to reason at a a bit higher lever, but they also forbid you 
to do few of the useful things that iterators can do.

In the end I think ranges were a success for D. Almost every part 
of the design of D has problems; sometimes even large problems 
(like shared, problems with missing head and tail const, missing 
logic constness, problems with scope, and so on at nauseum), but 
most times D ranges work, despite some faults they have.

Bye,
bearophile