add divrem and fldmod

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[oschulz]

@aplavin is this more "for completeness", or do you have specific use cases in mind? I'm not oppsed, just curious since Base.Fix2(divrem, x) would seem to be a rather special construction.

[aplavin]

The original motivation is to have div/mod setters in Accessors.jl. First I thought of just adding the corresponding math there, but InverseFunctions does look like the "proper" place for that. So, the plan is to have these inverses here, and then Accessors would just do like set(x, div, y) = set(x, divrem[1], y) (not actual code). Setting divrem would just work because of the inverse.

[oschulz]

Makes sense - @devmotion what do you think?

[devmotion]

I'm not sure. IIRC we don't define inverses for functions that return tuples so far? Do we want to support such functions? Should we start with more common functions such as eg. sincos first?

[oschulz]

inverses for functions that return tuples

Well, as long as the inverse function will take such a tuple as it's input it's fine I would say.

[aplavin]

Should we start with more common functions such as eg. sincos first?

Could also be useful, but it's not invertible...

Agree with code comments, will implement them. Thanks for the detailed review!

[aplavin]

bump

[oschulz]

bump

@devmotion

[oschulz]

@aplavin and @devmotion , is this close to merging? If so, I would hold off on a new release for this PR.

[oschulz]

@aplavin good to merge from your side?