Help with Ranges

[Charles]

Suppose I have the following line of code where arr is an array, 
doSomething is some predicate that does a lot of processing on 
each element, sort must come after the mapping, and there are 
more operations done to the range after sort:

arr.map!doSomething.sort. ...;

Sort fails to instantiate because the range it's receiving 
doesn't support element swapping. This may and might be resolved 
by calling array:

arr.map!doSomething.array.sort. ...;

However, this might trigger an allocation, and there's still more 
to do! Is there something I'm missing with regards to ranges that 
could help me make the first line work without using array, or is 
it more of an issue with my code's design?