[Haskell-cafe] Comments from OCaml Hacker Brian Hurt

Cale Gibbard cgibbard at gmail.com
Thu Jan 15 18:16:20 EST 2009

> If you're learning Haskell, which communicates the idea more clearly:
>  * Appendable
> or
>  * Monoid
> I can immediately figure out what the first one means.  With the second,
> I could refer to the GHC documentation, which does not describe what a
> Monoid does.  Or read a wikipedia article about a branch of mathematics
> and try to figure out how it applies to Haskell.

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. Modular addition, or multiplication
in some group is even farther from it.

More information about the Haskell-Cafe mailing list