head and tail methods for Mojo::Collection

[Grinnz]

Summary

Methods for Mojo::Collection to create new collections of the beginning or end of the collection.

Algorithms for the methods were adapted from List::Util::PP. We could just delegate to List::Util for XS functions but it would require List::Util 1.50.

Motivation

It can be useful to operate on the beginning or end of the collection during a chain without calculating slice indexes, and resulting in no extra undef elements when going past the original collection indexes.

References

#1350

[s1037989]

👍 Love it!

[kraih]

Like i said on IRC, it's pretty hard to justify adding so much code for a feature with such limited scope. Are there any good use cases related to Mojo::DOM or Mojo::Pg? Think i would be more ok with it if the methods were List::Util based one-liners and we were already depending on List::Util 1.50 for other reasons (like some of its other functions being used to improve Mojo::Parameters or similar).

[jhthorsen]

I guess range() would be sort of a competing feature? #1361

$c->range(-2) == tail
$c->range(0, 2) == head

[Grinnz]

range and head/tail would accomplish largely the same things. I'm not sure I can say which is clearer or nicer to use.

[marcusramberg]

I prefer #1361.

[kraih]

I just did some tests, and the pair functions in List::Util are very very slow. So that option of bumping the dependency is ruled out.

[kraih]

Since there have been no changes in some time, and the proposal is kinda complete. I'm just calling for a vote @mojolicious/core!

[kraih]

The feature seems useful, but i don't think it's useful enough to require so much code. So, i'll be voting neutral.

[kraih]

Maybe worth mentioning that Mojo::Collection::slice is deprecated now. So there is no alternative at all in the Mojo::Collection API anymore.

[jhthorsen]

Just as a reminder: #1361 was my alternative, but I closed it since there wasn’t any interest. I still think it’s a good idea to mimic JavaScript though.

[jberger]

I am in favor of both this and/or #1361. Sorry I'm late to the vote, vacation got in the way

[marcusramberg]

I think such a feature should exist, but guess I'm neutral to head/tail

_{Sent with GitHawk}

[kraih]

I've changed my vote to 👍, since there is a lot of interest in this functionality and i can't think of a more mojo-ish solution.