On 2005-02-28 at 20:22GMT Keith Wansbrough wrote:
The reason was that error messages for beginners' code were rather baffling. (And pretty baffling for some experts too!)
I don't understand how they could be more baffling than any other type errors involving monads. Can you give an example? (I could not find any, only mentions of them.) Maybe error messages were less clear then? Or maybe understanding of monads was less pervasive?
Beginners are taught lists and list comprehensions before they are taught monads. The errors they saw involved monads, which they didn't yet know about. Confusion reigned.
True, but it was still the wrong solution to the problem; Something involving a "beginners prelude" -- which would fit well with the idea of less in the standard prelude -- would avoid the annoyance that mplus isn't (++) and so on. I don't think it's too onerous to tell beginners that "you have to put import Didactic {- or whatever -} at the front of all Haskell programmes" ... followed several lectures later by "OK, I lied". Jón -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk