[thanatropism]

Sum types versus product types.

You’re doing

     data Number = Left Segment | Right Segment

but

     data Number = BothHands Segment Segment

is possible.

[cannabis_sam]

I just love how this illustrates the names sum and product types.

    permutations(sum of Segment) == permutations(Segment) + permutations(Segment) 

vs.

    permutations(product of Segment) == permutations(Segment) * permutations(Segment)

(Edit: permutations is the wrong term, it should be cardinality or a non-mathematical concept like some colloquial concept of “variations” )

[majewsky]

I don't think "permutations" is the right word. You probably want "cardinality".

[cannabis_sam]

You are right, I was thinking more from a programmers practical perspective and started with the word «varations» and changed it to «permutations» without thinking it through.

Thanks for the correction!