Document Range infix (elem), infix ∈

[treyharris]

The problem

infix:(elem) and its synonym infix:<∈> are not documented for Range.

Current behavior:

$ perl6
To exit type 'exit' or '^D'
> so (3 ∈ (0..10))
True
> so (3 ∈ (5..10))
False
> so (3 ∈ (0..Inf))
False
> so (3 ∈ (0..*))
False
> so (3 ∈ (-Inf..Inf))
False
> so (3 ∈ Int.Range)
False
> so (3 ∈ (*..*))
False

[lizmat]

I would argue that some of these results are incorrect

[JJ]

@lizmat that, too.

[treyharris]

I agree, too. But the operator needs to be documented regardless.

[Scimon]

The problem is all the Set operators on Ranges turn them into lists and then put that into a set.

Which works OK for Integers and Strings (ish) but less well for other.

This is why I started Range::SetOps which I really should get round to finishing (it doesn't handle a bunch of edge cases).

https://modules.raku.org/dist/Range::SetOps:cpan:SCIMON

On Tue, 28 Jan 2020 at 20:16, Trey Harris notifications@github.com wrote:

I agree, too. But the operator needs to be documented regardless.

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[2colours]

Actually, (elem) with Ranges on the right handside is implemented as a thing on its own, see https://github.com/rakudo/rakudo/blob/15df5d8a85406a92a9cbcb994e1d424029007f39/src/core.c/set_elem.pm6#L67

Anyway, the implementation of it is too naive; not necessarily better than a naive Set-coercion would be. Perhaps it should be improved before it can be documented.