Why does `filterBidirectional` exist, and why isn't it called `filter`?

[Paul Backus]

On Friday, 10 March 2023 at 13:46:03 UTC, Ogi wrote:
> On Thursday, 9 March 2023 at 17:07:40 UTC, Paul Backus wrote:
>>
>> I think probably you have to go on a case-by-case basis. 
>> `File.byLine`, for example, does not and should not precompute 
>> `front`, because doing so is potentially very expensive.
>
> And then ‘File.byLine’ ends up being const and now you can’t 
> call ‘front’ on it. Ouch.

Ranges already don't work with `const`, so the fact that this one 
fails to work with `const` a little more than usual is not a huge 
deal, IMO.