[Haskell] Re: Simple IO Regions

Dominic Steinitz dominic.steinitz at blueyonder.co.uk
Wed Jan 18 07:31:23 EST 2006

Simon Peyton-Jones <simonpj <at> microsoft.com> writes:

> I really like the way you use a set of constraints
> 	(IN m1 ms, IN m2 ms, IN m3 ms) 
> to maintain the set of marks.  Previously I've thought of using a nested
> tuple type
> 	(m1, (m2, (m3 ())))
> to maintain the set, but that is far less convenient.  Very neat.
> Why do you need the 
> 	instance IN () b
> ?

This makes me realise I understand this less than I thought. Can someone give 
an explanation of how the marks get built up?

Thanks, Dominic.

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