RE: [Haskell-cafe] nice simple problem for someone struggling....

21 Dec 2007

      Yes sorry....but this still fails with....

"`numberType1' is a rigid type variable bound by"

________________________________

From: Brent Yorgey [mailto:byorgey@gmail.com] 
Sent: 21 December 2007 17:29
To: Nicholls, Mark
Cc: Jules Bean; haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] nice simple problem for someone
struggling....

	"class ShapeInterface shape where
	       area :: shape->Int"

	now looks dubious....I want it to be something like

	"class ShapeInterface shape where
	       area :: Num numberType => shape->Int" ?

Rather, I think you probably want

class ShapeInterface shape where
    area :: Num numberType => shape -> numberType

-Brent