FW: RE [Haskell-cafe] Monad Description For Imperative Programmer

Bayley, Alistair Alistair_Bayley at invescoperpetual.co.uk
Thu Aug 2 07:17:07 EDT 2007

> From: haskell-cafe-bounces at haskell.org 
> [mailto:haskell-cafe-bounces at haskell.org] On Behalf Of peterv
> However, one thing which I find annoying is that a "classic 
> pure" function cannot evaluate an IO function unless you use 
> unsafePerformIO; one must "promote" (?demote) the pure 
> function into the IO monad.

That's just a property of the IO monad, rather than monads in general:

> Any ways of "promoting" such a pure function into the monadic 
> one automatically? I tried playing with "liftM", without succes.

This is where Claus plugs HaRe :-) (although liftM + friends is normally
what one uses). You might find this relevant:

Some people (but I'm not sure who) probably write most of their Haskell
code in a monadic style, so as to make conversion between various monads
less painful. It's still pure...

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