Adds entry_index to map.rs

[Thermatix]

I wanted a way to access the index but the only way to do that is by getting the entry and then the index from that which is mutable (and causes issues) or from get_full which returns more than what I needed so I added entry_index

[cuviper]

This seems good to me. Can you also add an equivalent method on IndexSet?

[Thermatix]

@cuviper, I'm sorry I haven't gotten back to you on this, I was sick over the last week and just genuinely forgot, I'll get on this as soon as I'm able!

[Thermatix]

Ok, Made the requested changes!

[cuviper]

Looks good, thanks!

[bluss]

Wait - this method seems underspecified and surprising? Both the PR and the doc comment needs to explain in detail what it does.

The method should not be called entry_* when it is more similar to get_full than to entry. I can guess that the motivation for adding this is performance, just having a simpler return type than get_full, is not enough to warrant inclusion.

[cuviper]

Well, at least it's not published yet if you want to change/revert it.

Yes, the main advantage I see is to avoid the indexing operation in get_full, which seems reasonable to me. The author originally called it get_index, which might be a better name, but that method already exists for using an index to get the key-value.

[bluss]

I am sorry for my tone there, that's certainly not pitch perfect, and extremely inappropriate for a "maintainer" that is as AWOL as I am.

Name doesn't need to be perfect, but it's clear that the current name is confusing, and it would be best to find a better doc comment or name before release - but it's not a requirement either.

[cuviper]

I opened issue #119 for this.