array to string functional?

[berni]

a) I've got an int[] which contains only 0 und 1. And I want to 
end with a string, containing 0 and 1. So [1,1,0,1,0,1] should 
become "110101". Of course I can do this with a loop and ~. But I 
think it should be doable with functional style, which is 
something I would like to understand better. Can anyone help me 
here? (I think a.map!(a=>to!char(a+'0')) does the trick, but is 
this good style or is there a better way?)

b) After having this I'd like to split this resulting string into 
chunks of a fixed length, e.g. length 4, so "110101" from above 
should become ["1101","01"]. Again, is it possible to do that 
with functional style? Probably chunks from std.range might help 
here, but I don't get it to work.

All in all, can you fill in the magic functional chain below?

> auto a = [1,0,1,1,1,0,1,0,1,1,1,1,0];
>
> auto result = magic functional chain here :-)
>
> assert(result==["1011","1010","1111","0"]);