RFC on range design for D2

[JAnderson]

Andrei Alexandrescu wrote:
> JAnderson wrote:
>>
>> Hi Andrei,
>>
>> I like the idea behind ranges.  I don't like C++'s / stl's long winded 
>> syntax at all.  Its so large that it generally uses up several lines 
>> along with several typedefs etc...  All that work just to iterate over 
>> some data.  The longer things get the more error prone they get... how 
>> many times have I put an begin when I meant to put end *sigh*.
>>
>> However I currently disagree on this point.
>>
>> Andrei Alexandrescu wrote:
>>  >
>>  > Fine. So instead of saying:
>>  >
>>  > foreach (e; c.all) { ... }
>>  >
>>  > you can say
>>  >
>>  > foreach (e; c) { ... }
>>  >
>>  > I think that's some dubious savings.
>>
>>
>> I think its useful to have the implicit range conversion.  Consider 
>> writing generic/template code.  Of course built in arrays could 
>> provide the .all but then consider passing around ranges.  That would 
>> also mean all ranges would also have a .all (could we go .all.all.all 
>> for instance?).
> 
> There's no regression. There are containers and ranges. Containers have 
> .all. Ranges don't.
> 
> I think you guys are making a good point; I'm undecided on what would be 
> better. One not-so-cool part about implicit conversion to range is that 
> all of a sudden all range operations spill into the container. So people 
> try to call c.pop and it doesn't compile. (Why?) They get confused.

I'm not sure that range operations need to spill over.  I was thinking
that foreach would be kinda like a template.  The foreach would do the
implict conversion. ie something like (pseudo):

foreach(I,T)(I i, T t, delegate d)
{
	foreach (I i; t.all)
	{
		d();
	}
}

Infact anything that takes range would implicitly convert (for they too
can be used inside generic code).  Of course that that would require
compiler support, probably.

> 
>> I'm all for compile time checking however I think that implicit .all 
>> (with of course an explicit option) will make it easy to change a 
>> function that once took an object to take a simple range  Also it 
>> would make it easy to change from one way of getting at a range to 
>> another.
>>
>> What about matrices?  They don't implement default .all, they would 
>> provide like .col and .row.
> 
> Bidimensional ones that is :o).
> 
> 
> Andrei