sorting API refactor using keywords

[StefanKarpinski]

Quoting the main commit:

The idea here is that the ordering and algorithm for sorting are two orthogonal parameters that have sensible defaults: neither, both or either can be independently specified. The resulting API is slightly more verbose but also somewhat more self-documenting.

Another sign that this might be on the right track is that this change reduces the LOC of base/sort.jl by 41 lines and reduces the method count of sort, for example, from 12 to 6.

Still needs deprecation methods before merging, but I thought I'd put it out there for feedback.

Note: I really wish that the lt and by ordering variations could be cleanly specified this way too – that would really cut the API down to a nice lean size without sacrificing any functionality. But I can't figure out a good way to do it.

[StefanKarpinski]

Ok, I took a crack at using keywords for by and lt as well and I really rather like the resulting API. It eliminates the need for sortby! and sortby – and generalizes naturally to other order-related functions without blowing up the export set or requiring the use of awkward types that really should be implementation details of the sorting code.

It has, however, revealed what seems to be a method dispatch bug. Will file an issue.

[stevengj]

@StefanKarpinski gets the hornéd hat of shame for checking this in without updating the documentation...

[ViralBShah]

I hate to do this.

+1

[StefanKarpinski]

I'm always wearing a horned hat of shame.

[GunnarFarneback]

This ought to give a deprecation message, I suppose:

julia> sort(>, [1:5])
ERROR: no method sort(Function,Array{Int64,1})

[StefanKarpinski]

Yes, thanks – I missed that one.