Re: [Haskell-cafe] What is a number. (Was: Num instances for 2-dimensional types)

And I agree that sometimes it can be suitable. But simply "defining an instance of Num" without a single word on the problem one is trying to solve is not just pointless. It's something that should not be done. On 5 Oct 2009, at 21:06, Lennart Augustsson wrote:

OK, "just pairs" have no arithmetic, but one way of defining arithmetic is to treat the pairs as complex numbers. Or as mantissa and exponent. Or as something else. So there's nothing wrong, IMO, to make pairs an instance of Num if you so desire. (Though I'd probably introduce a new type.)

On Mon, Oct 5, 2009 at 6:46 PM, Miguel Mitrofanov

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wrote:

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"Just pairs" have no natural arithmetic upon them.

Exactly my point.

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BTW. the missing term of M.M. is DUAL NUMBERS.

Remembered this already. Thanks anyway.

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