Stuart stugol at
Fri Jul 27 11:47:32 PDT 2012

On Friday, 27 July 2012 at 15:09:38 UTC, Graham Fawcett wrote:
> On Friday, 27 July 2012 at 13:10:46 UTC, Stuart wrote:
>> On Friday, 27 July 2012 at 03:00:25 UTC, Brad Anderson wrote:
>>> D equivalent: iota(0, int.max, 2).map!(a => /* do something 
>>> with even numbers */)();
>> I think you're missing the point. The purpose isn't to 
>> generate a sequence of numbers, but to illustrate how the 
>> Yield keyword is used in VB.NET. Sure, getting a sequence of 
>> numbers may be straightforward, but what about a 
>> lazy-populated list of all files on a computer? That can be 
>> done using Yield - and more importantly, WRITTEN like a normal 
>> synchronous function. Let's see you do that with map.
> That's easy:
>   [...elided code...]
>   auto entries = dirEntries(BASE_DIR, SpanMode.breadth);

Ah, but that depends upon the pre-existence of the dirEntries() 
function. I think perhaps you're missing the point - which is 
that "Yield" allows you to WRITE a function synchronously which 
will then be executed lazily, as an iterator. What you have 
demonstrated there is USING a lazy function. How would I write, 
in D, a function that would lazily assemble some data and return 
it as a lazy collection? I mean, without calling existing lazy 

Unless ranges (which I admit to knowing very little about) can do 
this, I respectfully request that Yield be supported in D.

> You should spend some time using ranges before drawing 
> conclusions about them.

Is there a good tutorial on them? I didn't see one on the website.

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