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You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Desugar list comprehension (mike h) ---------------------------------------------------------------------- Message: 1 Date: Wed, 2 Dec 2020 10:30:37 +0000 From: mike h <mike_k_hough...@yahoo.co.uk> To: beginners@haskell.org Subject: [Haskell-beginners] Desugar list comprehension Message-ID: <84d90b6c-8c1f-4eab-a573-38d1e3388...@yahoo.co.uk> Content-Type: text/plain; charset="utf-8" Hi, I have sumIs2020P1' xs = do x <- xs y <- xs guard (x + y == 2020) pure (x,y) which has been desugared from a list comprehension I would like to reduce this even more using >>= So I do sumIs2020P1'' xs = (a,b) where (a,b):rest = filter (\(x,y) -> x + y == 2020) pairs pairs = xs >>= \x -> xs >>= \y -> pure (x,y) but really I would like the guard to be within the >>= sections but I could not work out how to do it! i.e. I’m looking for something like (pseudo code) pairs = xs >>= \x -> xs >>= \y -> if (x + y == 2020) then pure (x,y) else DO_NOTHING which would then allow the filter to be removed. Many Thanks Mike Dr Mike Houghton mike_k_hough...@yahoo.co.uk -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.haskell.org/pipermail/beginners/attachments/20201202/bf9fb94f/attachment-0001.html> ------------------------------ Subject: Digest Footer _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners ------------------------------ End of Beginners Digest, Vol 149, Issue 1 *****************************************