Re: [Haskell-cafe] Thoughts about redesigning "Num" type class

Maybe it is unreasonable to look for maximal generality in use of each operator. A common use of "+" is for the operation of an abelian semigroup or monoid (any semigroup can be converted into a monoid anyway). Alexey. P.S. I was tempted to suggest "++" for cancellative monoids and "**" for arbitrary monoids, but "++" on lists is not quite cancellative if one of the lists is infinite. On Saturday, September 12, 2015 at 10:52:01 AM UTC+2, M Farkas-Dyck wrote:

On 11/09/2015, David Thomas javascript:> wrote:

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a subtraction operation that returns a different type

On 12/09/2015, Alexey Muranov javascript:> wrote:

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My 2 cents: the difference of two points in an affine space is a vector, the sum of a point of an affine space and a vector is another point.

This would mean multi-parametre type classes or type families, so we'd need to canonicalize them first, which seems unlikely in near future at least.