Georg Wrede wrote:
Not cosidering D or programming, the notion of a range implies a
beginning and an end.
Actually, not. Infinity is a primitive notion with ranges. A range that
defines empty like this:
enum bool empty = false;
is detected as infinite and treated accordingly by certain other ranges
and algorithms. See isInfinite in std.range.
So, in a certain sense, ranges could be
conceptualized as slices.
Yes, slices were a motivator and model for ranges.
All's well, and everything. But, things like input streams don't really
support the notion of "range", or "slice". They don't even want to.
Why don't they?
Sure, one could "coerce" or "forge" an input range to pretend some
manner of them, but that would be awkward at best, and laborios in
practice.
What would be a natural interface for an input range?
Does that mean that I'm against ranges? No. But there might be the
possibility that ranges are not a panacea. Just as Structured
Programming wasn't (look at Walter's gotos all over the place), OOP
wasn't, Functional Programming wasn't, or that metaprogramming doesn't
tell us whether God exists. Ranges solve some gargantuan problems in
Modern Programming, but I don't expect them to usurp a dozen of other
paradigms.
For sure nobody cracked them to be that great. I think you perceive them
as an imposition when they really are some rather unremarkable types
with at most a handful of primitives.
Could it be that the optimum would be to have /both/ ranges and, ehhh,
pointing notions?
Today, no sane programmer (outside of C or outside of Java) would make
his application /entirely/ ranges or /entirely/ classes.
I don't quite understand this. Ranges are a very simple abstraction for
iteration. They show how other iteration abstractions either were too
unsafe and verbose (C++/STL) or too bare-bones (C# iterators, Java
iterators, singly-linked lists used by functional languages), so in that
regard I think they hit the spot pretty nicely. Ranges are useful, but
hardly a be-all end-all. Thinking of building an application entirely of
ranges... I can't quite parse that.
Andrei
