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

[David Roundy]

On Fri, Jun 01, 2007 at 07:39:32PM +0100, Andrew Coppin wrote:
> David Roundy wrote:
> >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.
> >  
> 
> No, I mean... how could you use unsafePerformIO to perform a typecast? I 
> don't see a way to do that.

Then I'm confused.  What typecast are you talking about?
-- 
David Roundy
Department of Physics
Oregon State University