* Rijk J. C. van Haaften [2003-01-30 12:06 +0100]:

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* Rijk J. C. van Haaften [2003-01-30 11:41 +0100]:

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Recently, I came accross this expression: [ x + y | x <- xs | y <- ys ] ^ Put a comma ',' here.

That's something totally different. Two examples: 1. Comma [ x + y | x <- [1,2], y <- [3,4] ] = [4,5,5,6]

2. Bar [ x + y | x <- [1,2] | y <- [3,4] ] = [ x + y | (x,y) <- zip [1,2] [3,4] ] = zipWith (+) [1,2] [3,4] = [4,6]

The first is according to the standard. No problems so far. However, I couldn't find a description of the semantics of the second (and it is clearly non-standard), though I think the semantics given above using zip and zipWith are correct.

Ok, I see. Sorry, this was just my first thought. Unfortunately I cannot help you with the Bar thing. Regards, Olli -- obraun@ -+-[ informatik.unibw-muenchen.de ]-+-[ IIS _ INF _ UniBwM ] |-[ FreeBSD.org ]-+-[ FreeBSD Commmitter ] |-[ unsane.org ]-+-[ everything __ else ]

On 2003-01-30 at 11:08GMT Ross Paterson wrote:

On Thu, Jan 30, 2003 at 11:41:49AM +0100, Rijk J. C. van Haaften wrote:

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Recently, I came accross this expression: [ x + y | x <- xs | y <- ys ]

As far as I can see (Haskell Report), this is not allowed by the haskell 98 standard. So I assume it to be an ex- tension. Where can I find information about this?

It's not Haskell 98, but is implemented in GHC and Hugs (with extensions turned on).

As far as I can tell ghc 5.04 accepts this without complaint. Is this a bug, or should I pass some argument to turn extensions off? Jón -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk