Re: [Haskell-cafe] Very freaky

On Thu, 2007-07-12 at 14:07 -0700, Dan Piponi wrote:

On 7/12/07, Andrew Coppin wrote:

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Stefan O'Rear wrote:

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On Thu, Jul 12, 2007 at 07:19:07PM +0100, Andrew Coppin wrote:

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I'm still puzzled as to what makes the other categories so magical that they cannot be considered sets.

I thought I'd dive in with a comment to explain why category theory is an important subject and why it often crops up in Haskell programming. The key thing is this: in many branches of mathematics people draw what are known as commutative diagrams: http://mathworld.wolfram.com/CommutativeDiagram.html

So what do these diagrams represent?

Equations.

To a good approximation (and there is a certain amount of choice over which approximation you pick) Haskell also forms a category.

Haskell does form a category. To a good approximation Haskell forms a -nice- category.