Help with Ranges

[Charles]

On Monday, 27 July 2020 at 16:52:51 UTC, H. S. Teoh wrote:
> On Sun, Jul 26, 2020 at 07:10:41AM +0000, Charles via 
> Digitalmars-d-learn wrote:
>> 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. ...;
> [...]
>
> As Steven said, you cannot sort a range that doesn't support 
> swapping elements, and most ranges cannot unless they're backed 
> by actual storage, like an array. (*Something* has got to keep 
> track of where the elements are, after all.)

But in my example, isn't the output of map backed by actual 
storage? After all, it's taking in an array.

> In this particular case, though, if the contents of your 
> original doesn't need to be preserved, perhaps .schwartzSort 
> might be what you're looking for?
>
> If you cannot modify the original array for whatever reason, 
> then an allocation is probably unavoidable -- either you'll 
> have to create an array of your mapped elements, or you could 
> create an index and sort that instead (see .makeIndex or 
> std.range.zip for different approaches).
>
>
> T

I'll take a look at both of these, since I need to be aware of 
both cases. I'm trying to find the most efficient way of building 
a pipeline for my own betterment. Thank you.