Too complicated code for generating a random string?

[monarch_dodra]

On Saturday, 23 February 2013 at 16:29:49 UTC, Andrei 
Alexandrescu wrote:
> On 2/23/13 5:56 PM, monarch_dodra wrote:
>> On Saturday, 23 February 2013 at 14:28:28 UTC, Jens Mueller 
>> wrote:
>>> Can we have a generic function/code that is as efficient as 
>>> yours?
>>
>> Well, for now, we have "map" (and "iota"). This usually covers 
>> enough
>> ground, but there remains cases where it is sub-optimal.
>>
>> What we would need is a "generate". Basically, a range that 
>> calls a
>> function to generate the value of front on the fly. I've seen 
>> enough
>> threads like this one that "abuse" iota/repeat/take/map (or 
>> sequence and
>> recurrence for that matter), just to obtain a generic 
>> generator.
>>
>> Let's just write Generator/generator.
>
> Make sure you copy Sequence/sequence :o).
>
> Andrei

Have you actually tried it? Do you know what the signature of a 
function passed to sequence is?

I think this bug entry sums it up pretty well, and why "Sequence" 
is not really adapted:

http://forum.dlang.org/thread/bug-9550-3@http.d.puremagic.com%2Fissues%2F

//----
import std.stdio, std.range, std.conv, std.random, std.typecons;

void main()
{
     dstring letters = "abcd";
     dchar fun(Tuple!(), uint) {return letters[uniform(0, $)];}
     writeln(sequence!fun().take(9));
}
//----

I failed to use a lambda or mixin in this case.

I really don't think we should push to try to warp the existing 
stuff to work in any scenario, but rather, give the tools 
required to work intuitively for any scenario.