Impressed

[Nick Sabalausky]

On Thu, 26 Jul 2012 21:00:12 -0600
Brad Anderson <eco at gnuk.net> wrote:

> On Thu, Jul 26, 2012 at 7:56 PM, 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<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<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 equivalent: iota(0, int.max, 2).map!(a => /* do something with even
> numbers */)();
> 

Or:

foreach(i; iota(0, int.max, 2))
{
	// stuff
}

Or (not as fast, but more flexible):

foreach(i; iota(0, int.max).filter!(a => a%2==0)())
{
	// stuff
}

Or:

foreach(i; recurrence!(a => a[n-1] + 2)(0))
{
	// stuff
}

Etc...