join of range of ranges?

[Peter Alexander]

On Sunday, 22 September 2013 at 18:13:39 UTC, Peter Alexander 
wrote:
> On Sunday, 22 September 2013 at 14:26:14 UTC, bearophile wrote:
>>    auto r2 = [1, 2]
>>              .map!(x => [1, 2].map!(y => '*'))
>>              .join("_");
>
> The problem is that you are trying to map a range of range of 
> chars with a range of dchars.

This could also be solved by having join return an array of the 
CommonType of the elements of both ranges.