[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,

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