Re: [Haskell-cafe] Language extensions

On Wed, May 30, 2007 at 05:12:48PM +0200, Henk-Jan van Tuyl wrote:

On Wed, 30 May 2007 09:38:10 +0200, Tomasz Zielonka wrote:

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On Tue, May 29, 2007 at 09:43:03PM +0100, Andrew Coppin wrote:

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Henning Thielemann wrote:

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On Sun, 27 May 2007, Andrew Coppin wrote:

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But every now and then I discover an expression which is apparently not expressible without them - which is odd, considering they're only "sugar"...

Example?

Until I learned the trick of using lists as monads, I was utterly perplexed as to how to get a Cartesian product

This is far from not expressible: cart xs ys = concatMap (\x -> map ((,) x) ys) xs

A bit simpler is: cart xs ys = [(x, y) | x <- xs, y <- ys]

or: cart xs ys = do x <- xs y <- ys return (x, y)

I was responding to Andrew saying that computing cartesian product is apparently not expressible without list comprehensions. Best regards Tomek