Tnx. I read the document `generics.txt` before I started using the `concept` keyword.
Somehow I was under the impression concepts could be parameterized for me to refer to the contained value. Of course a container type may not even have `value` (it could be a function type or have a pair of values [if not a tuple]) while still being valid according to what I want. It would have been nice if I could do `T & T` or `T is Semigroup` because then `concept` does not need to know about the structure of contained types. Emmy looks interesting. It seems to extend the basic number types to be monoids under addition and multiplication (which they are). I already created `NumberSum`, `NumberProduct`, `LogicalOr` and `LogicalAnd` whose values are then under the their respective operation. I like how Emmy uses `zero` and `id` to denote identity for addition and multiplication. In a C library I wrote I called it `sum_identity` and `product_identity`. I would like something like `zero`, `one` or `id`, `half`, `double` to be standard.
