[Haskell-cafe] Comments from OCaml Hacker Brian Hurt

[Max Rabkin]

On Thu, Jan 15, 2009 at 3:16 PM, Cale Gibbard <cgibbard at gmail.com> wrote:
> However, "Appendable" carries baggage with it which is highly
> misleading. Consider, for instance, the monoid of rational numbers
> under multiplication (which, by the way, is quite useful with the
> writer transformed list monad for dealing with probabilities) -- you
> can claim that multiplication here is a sort of "appending", perhaps,
> but it's not really appropriate.

It's rather funny that there's a mathematical sense in which all
monoid operations *are* appending. The free monoid on a set has
appending as its operation, and the free monoid is initial in the
category of monoids on that set (by definition), so all monoid
operations are appending, modulo some equivalence relation.

:)

--Max