On Fri, Jun 21, 2002 at 12:50:21PM +0100, Simon Peyton-Jones wrote:
| From: Jon Fairbairn [mailto:Jon.Fairbairn@cl.cam.ac.uk] | Sent: 20 June 2002 16:27 | To: Simon Peyton-Jones | Subject: Library report, monad zero laws | | The old report used to include | | m >> zero = zero | zero >>= m = zero | m ++ zero = m | zero ++ m = m | | after the other monad laws. Now mzero and mplus are in the | library, shouldn't there be some mention of these laws there? | I'd be particularly keen to see a remark about | | _|_ >> zero | | inevitably being _|_
Would you put that next to m >> zero = zero ?
Well, that's rather the point. At the moment the library report just says "The class methods mzero and mplus are the zero and plus of the monad.", which implies m >> zero = zero, but it can't be. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk 31 Chalmers Road jf@cl.cam.ac.uk Cambridge CB1 3SZ +44 1223 570179 (after 14:00 only, please!)