[Haskell-beginners] WWAAA... I hate monads
wagner.andrew at gmail.com
Wed Apr 22 06:55:49 EDT 2009
Here's a clearer description:class Monad m where
return :: a -> m a
(>>=) :: m a -> (a -> m b) -> m b
Instances of Monad must satisfy the following laws:
return a >>= k == k a
m >>= return == m
m >>= (k >>= h) == (m >>= k) >>= h
Much more clear and concise, don't you think?
On Wed, Apr 22, 2009 at 6:21 AM, Daniel Carrera <
daniel.carrera at theingots.org> wrote:
> I hate monads.
> I love 90% of Haskell. The functional stuff is beautiful, easy to
> understand, crystal clear, elegant, etc. But I'm having a mighty hard time
> getting my head around monads. Consider the following explanation of a
> "A monad is represented as a type constructor (call it m), a function that
> builds values of that type (a -> m a), and a function that combines values
> of that type with computations that produce values of that type to produce a
> new computation for values of that type".
> 1) I know what a type is, but not a "type constructor". I don't normally
> think of an Int or even a complex type as being "constructed" except in the
> sense of OOP which I know is not what the author means.
> 2) Just *read* the paragraph... "a type constructor, a function that builds
> value of that type, and a function that combines values of that type with
> computations that produce values of that type to produce a computation of
> values of that type" Ugh....
> Can anyone recommend a simple and clear explanation of monads? You can
> assume that I know basic math and basic Haskell syntax. So, for example, "a
> -> b" is much more clear than "a function that takes input of one type and
> has an output of a different type".
> Any help would be appreciated.
> Beginners mailing list
> Beginners at haskell.org
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