[Haskell] Broken monad laws

Sean Seefried sseefried at cse.unsw.edu.au
Wed Nov 23 20:55:20 EST 2005

On 24/11/2005, at 9:45 AM, Iavor Diatchki wrote:

> Hello,
> I just noticed that the GHC/Hugs "standard" libraries have acquired a
> list monad transformer, which is broken, because it does not satisfy
> the associativity law when applied to non-commutative monads.  I am
> not referring to some corner-case strictness problem, but rather a
> fairly well known result.  The associativity law is important, because
> without it the 'do' notation can be very confusing.  Bellow is an
> example, for people not familiar with the porblem.
> -Iavor

This seems to have been discussed already:



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