Julia: Linspace defaults the `n` parameter to 50

[yurivish]

I was surprised when I found that Julia's linspace function uses the number 50 as the default argument for the number of steps:

linspace(start, stop, n=50)

Discussion on Slack indicated that this behavior comes from SciPy, but that it should probably be dropped for 0.7.

[JeffBezanson]

Agreed; that seems like a pretty arbitrary default value.

[fredrikekre]

What would be a better default value? Or is the idea that we shouldn't have a default value at all?

[nalimilan]

No default makes sense for this function IMHO.

[lobingera]

btw: on matlab 100

[timholy]

@yurivish, let me know if you intend to submit a PR, otherwise I will do it.

Relatedly, logspace has a default base of 10. I'm inclined to say it's fine to keep this.

[yurivish]

@timholy submitted: https://github.com/JuliaLang/julia/pull/24805

I noticed that logspace also had the default value 50 for its n argument so I changed that in the above PR, for the same reasons we decided to remove it from linspace.

Unrelatedly, I noticed that the actual parameter for linspace is called len in the code, though it's n in the docs — should I file a separate PR for that? I'd guess len is the more descriptive name.