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

That is OK. Since understand the basic concept of monoid (I mean the thing in actual math), the idea here is totally not hard for me. But the sample here does not show why (or how) we use it in programming, right? On Sat, Nov 14, 2009 at 12:48 AM, Stephen Tetley wrote:

2009/11/13 Rafael Gustavo da Cunha Pereira Pinto :

...

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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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