G'day all.
Slight nit...
Quoting ok <[EMAIL PROTECTED]>:
I've been thinking about making a data type an instance of MonadPlus.
From the Haddock documentation at haskell.org, I see that any such
instance should satisfy
mzero `mplus` x = x
x `mplus` mzero = x
mzero >>= f = mzero
v >> mzero = mzero
As discussed previously, that last "law" is wrong. In particular, it
can't be true of any monad transformer:
lift fireMissiles >> mzero /= mzero
but is that all there is to it? Are there no other requirements for
MonadPlus to make sense?
It's proposed to split nondeterminism-like monads and error catch-like
monads to allow for some other laws:
http://haskell.org/haskellwiki/MonadPlus_reform_proposal
Cheers,
Andrew Bromage
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