Successively prepending to slices.

[bearophile]

dnspies:

> efficiently, or is it better to avoid this sort of thing?

D arrays are dynamic on the right. So appending on their left is 
not efficient (also here you are not prepending, you are 
concatenating. Array concatenation creates a new array). In some 
cases you can append on the right many items and then use 
std.algorithm.reverse (don't forget the () if you use UFCS) to 
reverse them. In case of doubt write little benchmarks.

Bye,
bearophile