[Haskell-cafe] Re[2]: strict Haskell dialect
Wolfgang Jeltsch
wolfgang at jeltsch.net
Sat Feb 11 07:17:12 EST 2006
Am Sonntag, 5. Februar 2006 17:36 schrieb Bulat Ziganshin:
> [...]
> each and every monadic operation is a function!
What do you mean with "monadic operatation"? (>>=), (>>) and return are, of
course, functions but an I/O action like getChar is *not* a function. Also a
list is not a function but a value of the list monad.
> type "IO a" is really "RealWorld -> (RealWorld,a)"
This representation is just there to help people understand what I/O is but
actually, IO a is a type which is not implementable in ordinary Haskell and
therefore cannot be a function. In addition, RealWorld -> (RealWorld,a) as
an explanation of what IO a is has its limitations. If we run an I/O action,
we aren't just interested in the final state but also in intermediate states.
> and the same for any other monad. concept of the monad by itself means
> carrying "hidden" state from one monadic operation to the next.
That's too specific. A list, for example, doesn't have to do anything with
state and [a] is not represented as a function.
> [...]
Best wishes,
Wolfgang
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