Impressed

[Nick Sabalausky]

On Fri, 27 Jul 2012 03:56:32 +0200
"Stuart" <stugol at gmx.com> wrote:

> On Friday, 27 July 2012 at 00:10:31 UTC, Brad Anderson wrote:
> > D uses ranges instead of iterators. You can read more about 
> > them here: http://ddili.org/ders/d.en/ranges.html
> >
> > I find ranges to be a vast improvement over iterators 
> > personally (I use iterators extensively in C++ for my job and 
> > lament not having ranges regularly).
> >
> >
> On Friday, 27 July 2012 at 00:17:21 UTC, H. S. Teoh wrote:
> > D has something far superior: ranges.
> >
> > 	http://www.informit.com/articles/printerfriendly.aspx?p=1407357&rll=1
> >
> > Even better, they are completely implemented in the library. No
> > unnecessary language bloat just to support them.
> 
> I'm not very well up on ranges. I understand the general [1 ... 
> 6] type of ranges, but I really don't see how custom range 
> functions could be as useful as the Yield support in VB.NET. I 
> mean, here's an example of an iterator in VB.NET:
> 
>     Public Function InfiniteSequence(StartValue As Int32, Step As 
> Int32) As IEnumerable(Of Int32)
>        Do
>           Yield StartValue
>           StartValue += Step
>        Loop
>     End Function
> 
> Usage:
> 
>     For Each N in InfiniteSequence(2, 2)
>        ... do something with this sequence of even numbers ...
>     Next
> 
> Notice how this function is written like a synchronous loop, yet 
> yields a lazy-initialised infinite sequence of numbers. Granted, 
> it's not a particularly useful example, but trust me: Iterators 
> and Yield in .NET is *really* damn useful. I would go so far as 
> to say it was one of the language's best features.
> 
> I may be wrong, but it looks like I'd have to code a new class - 
> not to mention several specific functions and some kind of state 
> variable - just to simulate this functionality in D. Can anyone 
> clarify this for me?

D can do that with either fibers or opApply. I've explored all the
different approaches in this admittedly not-so-well-written article:

https://semitwist.com/articles/article/view/combine-coroutines-and-input-ranges-for-dead-simple-d-iteration

Note, however, that fibers (while far, *far* faster than
threads) are still too heavyweight to be recommended for most
generator functions (as I learned after writing that article). So if you
want a generator, you should use opApply instead of fibers or my
"InputVisitor" trick. I'd recommend using Adam's trick mentioned in the
second "Update" at the bottom of the article.