I originally didn't have the package exporting those things.
I would be amenable to standardization without them, but I use them in about
20 packages that are built on top of semigroups, and naturals and non-empty
lists come up when talking about semigroups a lot.
Rather than having them live way up in extension land with the rest of my
algebra libraries i moved them down to where they could do some good and
admit some optimizations.
On Sun, Aug 14, 2011 at 2:21 PM, Chris Smith
On Sun, 2011-08-14 at 21:05 +0300, Yitzchak Gale wrote:
Brandon Allbery wrote:
Anything useful has to be modified to depend on SemiGroup as well to get mconcat or its replacement; that's why you jumped the proposal to begin with....
Not at all. Types with Monoid instances need an additional instance, a Semgroup instance
That does require depending on semigroups though, and I think that's what Brandon was saying.
Of course, the obvious solution to this would be to promote semigroups, e.g., by adding it to the Haskell Platform or including it in base... but the current semigroups package is a bit heavyweight for that; it exports four new modules for what is really a very simple concept!
-- Chris Smith
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