[Haskell-cafe] Design Patterns by Gamma or equivalent

Colin Paul Adams colin at colina.demon.co.uk
Tue Mar 17 05:54:59 EDT 2009

>>>>> "Wolfgang" == Wolfgang Jeltsch <g9ks157k at acme.softbase.org> writes:

    Wolfgang> By the way, the documentation of Control.Category says
    Wolfgang> that a category is a monoid (as far as I remember). This
    Wolfgang> is wrong. Category laws correspond to monoid laws but
    Wolfgang> monoid composition is total while category composition
    Wolfgang> has the restriction that the domain of the first
    Wolfgang> argument must match the codomain of the second.

I'm reading the Barr/Wells slides at the moment, and they say the

"Thus a category can be regarded as a generalized monoid, or a
'monoid with many objects'"
Colin Adams
Preston Lancashire

More information about the Haskell-Cafe mailing list