Proposing std.typecons : Optional (with PR)

[FeepingCreature]

On Tuesday, 11 June 2019 at 09:58:48 UTC, aliak wrote:
> If we're going to put an optional type there, I would consider 
> not copy pasting nullable as it has some other issues as well, 
> and maybe nail the interface down properly? E.g. having an 
> optional that's a range would be rather awesome. Have you 
> looked at: https://code.dlang.org/packages/optional. It has a 
> lot of other added features as well but those can be removed if 
> they're too much.

I've looked at that and I specifically disagree with the decision 
to make it a range; that's why I didn't just internally switch to 
dub optional. Ranges are not monads. We may wish we had a concept 
of monads but we don't; ranges are not a general replacement for 
any conceivable container. `Optional.front` is just *weird* and 
unintuitive at first glance. It's not a bad decision in 
isolation, but it doesn't fit what I consider "the D style" of 
type design.

Sorry if that explanation is too fuzzy.