Should String/Array.slice accept 0 as an end argument

[dannyob]

It seems very weird that you can easily slice from the start of a String or Array, but not to its end:

> String.slice 0 3 "Hello"
"Hel" : String

> String.slice 0 -1 "Hello"
"ell" : String

> String.slice -3 -1 "Hello"
"ll" : String

-- But how do we get "lo"?
> String.slice -2 0 "Hello"
"" : String

I think this is a side effect of Elm borrowing from Python -- Python slice indices can be negative, but they can also be None, which indicates either the start or the end of the list, depending on where they are used.

Conceivably we could use 0 as an end argument for this function, just as 0 as a start argument means "before the start." But it's all feeling a bit like null values here...

It feels like @sindikat might have some thoughts on this...

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[andreaazzini]

The slice functions behave exactly like their Javascript counterparts. IMHO, it wouldn't be right to make the Elm slice work differently. You can (and probably should) use the String.right function in this specific case.

> String.right 2 "Hello"
"lo" : String

However, the right function is not available in the Array module. Maybe we should discuss how to avoid this specific asymmetry.

[andreaazzini]

The slice functions behave exactly like their Javascript counterparts. IMHO, it wouldn't be right to make the Elm slice work differently. You can (and probably should) use the String.right function in this specific case.

> String.right 2 "Hello"
"lo" : String

However, the right function is not available in the Array module. Maybe we should discuss how to avoid this specific asymmetry.

[evancz]

Added to #322 that tracks all these ideas in one place. That way we can try to make more coherent API choices so things match across all core libraries.

[evancz]

Added to #322 that tracks all these ideas in one place. That way we can try to make more coherent API choices so things match across all core libraries.