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digitalmars.D - Dithering about ranges

reply Georg Wrede <georg.wrede iki.fi> writes:
Not cosidering D or programming, the notion of a range implies a 
beginning and an end. So, in a certain sense, ranges could be 
conceptualized as slices.

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.

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.


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.

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.
May 21 2009
next sibling parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
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 

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
May 21 2009
prev sibling parent reply Steve Teale <steve.teale britseyeview.com> writes:
Andrei Alexandrescu Wrote:


 I don't quite understand this. Ranges are a very simple abstraction for 
 iteration. They show how other iteration abstractions either were too 

 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


Andrei,

I'm still waiting to read the definitive article about ranges. Does this exist
at present? It's nice to have something like an RFC, not just a new version of
a standard library without warning, and just depend on the comments. As Walter
has I think said, comments always lie!

Steve
May 22 2009
parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
Steve Teale wrote:

 Andrei Alexandrescu Wrote:
 

 I don't quite understand this. Ranges are a very simple abstraction
 for iteration. They show how other iteration abstractions either

 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


 
 Andrei,
 
 I'm still waiting to read the definitive article about ranges. Does
 this exist at present? It's nice to have something like an RFC, not
 just a new version of a standard library without warning, and just
 depend on the comments. As Walter has I think said, comments always
 lie!
 
 Steve


Other people have explained this once, but allow me to repeat. There was 
a lengthy RFC period with discussions on the announce group entitled 
"RFC on range design for D2" supported by a document. That document has 
been since superseded by the implementation documentation which, aside 

you need to define and use ranges effectively.

There was a lengthy "warning breaking changes coming" period, to the 
extent that some people on the group got tired of it.

If you are interested in ranges, the one thing you shouldn't be doing is 
to wait for a tutorial written by yours truly. What you could be doing 
in little more than the time it takes to write a long post (ahem) would 
be to grok ranges yourself and write a solid tutorial about ranges in a 
blog, web page, or online magazine. They are deceptively simple and can 
be composed in very interesting ways.

Waiting for something from Walter or myself is not the pattern to be in. 
Shin, Don, Jarrett, David, and others are doing great stuff, and 
incidentally don't whine as much (except for Jarrett -- squeaky wheel 
gets the K-Y).


Andrei
May 22 2009