[Haskell-cafe] Just for a laugh...

David Roundy droundy at darcs.net
Fri Jun 1 14:36:46 EDT 2007

On Fri, Jun 01, 2007 at 07:28:07PM +0100, Andrew Coppin wrote:
> David Roundy wrote:
> >Note also that you can use unsafePerformIO to safely get pure functions
> >doing both these operations.
> >  
> I've always been puzzled by this one... how does unsafePerformIO 
> circumvent the type system? I don't understand.

It's a primitive.  You couldn't implement it unless you're the
compiler-writer.  But it's a necesary primitive, if you wish to build
efficient data types.  You just need to carefully audit everywhere that
unsafePerformIO is used.
David Roundy
Department of Physics
Oregon State University

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