[Haskell-cafe] Re: evaluation semantics of bind

mail at justinbogner.com mail at justinbogner.com
Thu Feb 5 11:26:16 EST 2009

Gregg Reynolds <dev at mobileink.com> writes:
> I think I've just about got monads figured out, but there's one detail that
> still escapes me.  As I understand it, a monad is a kind of programming trick
> the uses data dependency to force evaluation order.  x >>= f means apply f to
> x; since the value of f x depends on the value of x, the evaluator must
> evaluate x before f x. However, consider:
>     getChar >>= \x -> getChar

x >>= f does not mean "apply f to x", it means "do x, and then do f with
the result of x". Bind is a sequencing operator rather than an
application operator.

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