[Haskell-cafe] List Monads and non-determinism
timon.gehr at gmx.ch
Sat Jul 20 01:27:12 CEST 2013
On 07/20/2013 12:58 AM, Matt Ford wrote:
> Thanks for the help.
> I thought >>= was left associative? It seems to be in the examples from
> Learn You A Haskell.
Yes, >>= is left-associative. The associativity of >>= is not relevant
for your example because no two >>= operations actually occur next to
each other. The second >>= is part of the lambda occurring as the second
argument to the first >>=. Lambdas bind 'the rest of the expression'.
[1,2] >>= \n -> [3,4] >>= \m -> return (n,m)
is equivalent to:
let a = [1,2]
b = (\n -> [3,4] >>= \m -> return (n,m))
in a >>= b
> I tried to use the associative law to bracket from the right but it
> didn't like that either...
> [1,2] >>= (\x -> (\n -> [3,4])) x >>= \m -> return (n,m))
> Any thoughts?
Where does that 'x' come from?
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