Dimitri Fontaine wrote:
Then there's the metric space which is a data type with a distance
function. This function must be non-negative, commutative, etc.
So I guess what we need here is a Operator Group to define our plus and
minus operators, and the fact that it's a group says (by convention,
like the total ordering of a BTree) that the + is commutative and the -
its opposite. Or we have an "option" called abelian for specifying the
commutativity?
Would the group analogy work with partially ordered domains, e.g. with a
location on a sphere datatype together with an identifier for the sphere
- so poi on earth can be compared to another, but not a poi on earth
with a poi on the moon. ?
regards,
Yeb Havinga
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