Does anyone know a construct to turn a lambda into an infinite range.

    import std.random;

    unittest
    {
        Random gen;
        foreach(v; xxx!(() => uniform(0, 100, gen)).take(10))
            writeln(v);
    }

I though I've seen this around somewhere but can no longer find it.

On Monday, 29 September 2014 at 17:02:43 UTC, Martin Nowak wrote:
> Does anyone know a construct to turn a lambda into an infinite range.
>
>     import std.random;
>
>     unittest
>     {
>         Random gen;
>         foreach(v; xxx!(() => uniform(0, 100, gen)).take(10))
>             writeln(v);
>     }
>
> I though I've seen this around somewhere but can no longer find it.

I can't find anything to do it. That seems weirdly absent.  You can abuse recurrence to do it.


    Random gen;
    foreach(v; recurrence!((a, n) => uniform(0, 100, gen))(0).dropOne.take(10))
        writeln(v);

On Monday, 29 September 2014 at 17:02:43 UTC, Martin Nowak wrote:
> I though I've seen this around somewhere but can no longer find it.

AFAIK, this as never existed.

We recently merged in "cache" into phobos. This seems like a prime candidate to expand to also take a function/delegate, as on of its built-in feature is that the value of "front" is not changed until "popFront()" is called. Having it also accept a function/delegate would make sense.

The issue with *not* having that is that a "dumb" adapter would fail the:
r.front == r.front
Test. And I'm pretty sure this test is expected to pass, even for the so called "transient" ranges.

I think I'll get to it now (this week).

Thoughts?

V Mon, 29 Sep 2014 19:02:36 +0200
Martin Nowak via Digitalmars-d-learn
<digitalmars-d-learn@puremagic.com> napsáno:

> Does anyone know a construct to turn a lambda into an infinite range.
> 
>      import std.random;
> 
>      unittest
>      {
>          Random gen;
>          foreach(v; xxx!(() => uniform(0, 100, gen)).take(10))
>              writeln(v);
>      }
> 
> I though I've seen this around somewhere but can no longer find it.

http://dlang.org/phobos/std_range.html#.Repeat ?

On Monday, 29 September 2014 at 21:16:27 UTC, Daniel Kozák via Digitalmars-d-learn wrote:
> V Mon, 29 Sep 2014 19:02:36 +0200
> Martin Nowak via Digitalmars-d-learn
> <digitalmars-d-learn@puremagic.com> napsáno:
>
>> Does anyone know a construct to turn a lambda into an infinite range.
>> 
>>      import std.random;
>> 
>>      unittest
>>      {
>>          Random gen;
>>          foreach(v; xxx!(() => uniform(0, 100, gen)).take(10))
>>              writeln(v);
>>      }
>> 
>> I though I've seen this around somewhere but can no longer find it.
>
> http://dlang.org/phobos/std_range.html#.Repeat ?

That just repeats the value, but doesn't re-evaluate the value on every call to front/popFront.

On Monday, 29 September 2014 at 20:02:19 UTC, monarch_dodra wrote:
> I think I'll get to it now (this week).

I threw something together, and it really works exceptionally
well. Will file PR soon.