[Haskell-cafe] Could someone teach me why we use Data.Monoid?

[Stephen Tetley]

2009/11/13 Rafael Gustavo da Cunha Pereira Pinto <RafaelGCPP.Linux at gmail.com>:
>
> Monoid is the category of all types that have a empty value and an append
> operation.
>

Or more generally a neutral element and an associative operation:

The multiplication monoid (1,*)

9*1*1*1 = 9

1 is neutral but you might be hard pressed to consider it _empty_.


Best wishes

Stephen