SeeWebsiteToContactMe at semitwist.com
Thu Jul 26 20:21:54 PDT 2012
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 */)();
foreach(i; iota(0, int.max, 2))
Or (not as fast, but more flexible):
foreach(i; iota(0, int.max).filter!(a => a%2==0)())
foreach(i; recurrence!(a => a[n-1] + 2)(0))
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