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monet / monet.js

monet.js - Monadic types library for JavaScript
https://monet.github.io/monet.js/
MIT License
1.6k stars 114 forks source link

Add List and NEL .lookup #241

Closed mlrv closed 3 years ago

mlrv commented 3 years ago

Add List.lookup(i) and NEL.lookup(i) for safe access at index, should be good enough to close #229.

Note that I decided to treat undefinedvalues as missing, not sure whether that's the right decision or not, happy to hear feedback on this.

ulfryk commented 3 years ago

@mlrv I'm not sure if it's worth investing time as for now there is a decision to drop support for List and NEL in version 1.0.0 in favour of some small library allowing integration with https://github.com/immutable-js/immutable-js collections.

ulfryk commented 3 years ago

But anywy - it's good to have it for now. And It would be great fi you can also add nth() that would return value as is ( undefined if it's >= than length ). That gives end user enough flexibility :)

mlrv commented 3 years ago

But anywy - it's good to have it for now. And It would be great fi you can also add nth() that would return value as is ( undefined if it's >= than length ). That gives end user enough flexibility :)

Ah sure, makes sense 👍 It's not a lot of work, so it shouldn't be a big deal if this stuff gets removed in a later release.

In terms of nth, I'm not really sure, isn't that against the fundamental principles of this (or any other FP) library? It's trivial to implement of course, but I wonder if it's not just a way to help developers shoot themselves in the foot. Happy to be contradicted of course :)

ulfryk commented 3 years ago

I'm not really sure, isn't that against the fundamental principles of this (or any other FP) library?

I think it's good to allow users to opt-out of wrapping null / undefined elements (this is the cost of the decision made to not allow Some to contain null | undefined 🙃 ).

mlrv commented 3 years ago

Mmmh I can see the CI failing, makes sense. Should we rather have nth return null? Not that it makes much difference, as long as it's documented, but given the nature of the function and how close it is to just a normal index access, I would expect it to return undefined in those circumstances

ulfryk commented 3 years ago

Yes, undefined is ok. I believe you can suppress eslint for those 2 lines, as it's a valid place to ignore the rules :)