Add linspace_exclusive function.

[Kwonunn]

Add a linspace_exclusive function which creates a Linspace iterator which is exclusive at its upper bound. This is essentially the same as linspace(endpoint=False) in numpy.

Addresses #1169

[Kwonunn]

If this is a welcome addition I'll add some tests and an equivalent for logspace.

I thought about using std::ops::Range as the argument for a new linspace function, which would allow something like:

let a = linspace(0.0..10.0, 32); // exclusive
let b = linspace(0.0..=50.0, 32); // inclusive

I think this is nicer and more idiomatic, but I don't see a good way of adding it that doesn't also break backwards compatibility.

[nilgoyette]

I think this is nicer and more idiomatic

Interesting. I do find it nicer, but this is only my opinion. What's cool is that the same name could be reused instead of creating new names like linspace_exclusive. I'm gonna need @akern40 opinion on this matter.

[akern40]

Strongly agree, I love this approach, so my question is how we can make a smooth transition (or we'll just have to make a warning somehow?)

[Kwonunn]

Since Rust doesn't do function overloading there really are only two options:

1. Make a new function with a name like linspace_range, put a deprecation warning on the old one and tell people to migrate over.
2. Change the function signature of linspace, which would be a backwards-incompatible change.

I don't know how opposed you are to these kinds of API changes, I'll leave it to you to decide.