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Re: ANN: intervalset Was: Set type for datetime intervals

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  Re: ANN: intervalset Was: Set type for datetime intervals Random832 <random832@fastmail.com> - 2016-04-04 11:44 -0400

#106449 — Re: ANN: intervalset Was: Set type for datetime intervals

On Mon, Apr 4, 2016, at 11:32, Oscar Benjamin wrote:
> On 4 April 2016 at 16:09, Random832 <random832@fastmail.com> wrote:
> > Like I said before, I don't think the set-like operations on Intervals
> > are useful - what can you accomplish with them rather than by making a
> > set consisting of only one interval and doing operations on that?
> 
> I guess it depends what your application is but sympy has interval
> sets and can do computation on them to represent the solutions of
> equations/inequalities (many other types of set are also included).

Yes, my question is why it's useful to have a single Interval as a
*distinct* type, separate from the interval set type, which supports a
sharply limited number of set-like operations (such as the union of two
overlapping intervals but NOT two non-overlapping ones). This doesn't
appear to be the case in sympy based on your examples.

Having an interval as a distinct type may be useful (to iterate over the
intervals of a set, for example), but his design blurs the line between
intervals and sets (by supporting some set operations) without
eliminating it as sympy seems to do.

> In [6]: Interval(1, 2) | Interval(3, 4)
> Out[6]: [1, 2] ∪ [3, 4]
> 
> There is some discussion about why it's good to do this stuff with
> sets (for sympy's purposes here):
> http://docs.sympy.org/latest/modules/solvers/solveset.html#why-do-we-use-sets-as-an-output-type

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