Optimize scanr for improved performance

[usefulmove]

This pull request addresses the TODO comment in the code to further optimize the scanr algorithm. The function has been refactored to run foldl on a reversed version of the input list, rather than use foldr as did the previous implementation. The optimized version also makes use of cons to add to the accumulator list, rather than call convert the added element to a separate list and using append.

The performance analysis detail is below. The test was performed by calling the scanr function on a 2,000,000 element list for 50 cycles.

• original scanr: CPU Time: 20,720 ms | Real Time: 20,733 ms | GC Time: 15,265 ms
• optimized scanr: CPU Time: 4,226 ms | Real Time: 4,231 ms | GC Time: 2,701 ms

All raco unit tests have been run successfully.

Note: The original implementation made use of the first function. The testing showed that this increased execution time by about 26%. However, I want to acknowledge that there may be a reason that this is preferred that I am not aware of. I believe the difference is due to first implementing a guard to ensure it is only called on lists while car is missing the same guard.

Please do with this request as you like. I am a fan of this library, and I was hoping to help.

[codereport]

@usefulmove This looks great! Are you able to rebase on master / target it to master? It looks like you are targeting a "open-issues" branch from long time ago.

[usefulmove]

Yes, of course. I'll do that today. - Duane -

…

On Tue, Apr 2, 2024 at 7:36 AM Conor Hoekstra ***@***.***> wrote: @usefulmove <https://github.com/usefulmove> This looks great! Are you able to rebase on master / target it to master? It looks like you are targeting a "open-issues" branch from long time ago. — Reply to this email directly, view it on GitHub <#29 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/APO5WT2A6P2QO7FMBGBMRSLY3K67HAVCNFSM6AAAAABFSRSVNGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMZSGIYTMOJVGA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[usefulmove]

Yes, of course. I'll do that today. - Duane -
…
On Tue, Apr 2, 2024 at 7:36 AM Conor Hoekstra @.> wrote: @usefulmove https://github.com/usefulmove This looks great! Are you able to rebase on master / target it to master? It looks like you are targeting a "open-issues" branch from long time ago. — Reply to this email directly, view it on GitHub <#29 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/APO5WT2A6P2QO7FMBGBMRSLY3K67HAVCNFSM6AAAAABFSRSVNGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMZSGIYTMOJVGA . You are receiving this because you were mentioned.Message ID: @.>

The pull request should now target master.

[codereport]

🔥 👍