Too complicated code for generating a random string?

[jerro]

> BTW, I think the clearest remains my generator proposal:
> string randomString =
>     fastGenerator!(() => letters[uniform(0, $)]).take(9).array;

If the goal was to replace iota(n).map, it may be better to just 
have something like:

     generate!(() => letters[uniform(0, $)])(n).array

But of course, your fastGenerator is more general. I personally 
don't often have a need to generate an infinite range in this 
way, but other people may.

> Any chance you could tell me how it fares in your bench?

I used this code:

auto tmp = FastGenerator!(() => letters[uniform(0, 
$)])().take(n).array;

When I build it with GDC, it performs about the same as the code 
that uses iota and map. When I build it with DMD it's about 10% 
slower than the code that uses iota and map. It seems that DMD 
fails to inline the lambda in this case.

By the way, this is not a very good benchmark for ranges because 
most of the time is spent generating random numbers.