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

21 Dec 2007

      Really....I'm sure I tried that...(as it seemed obvious) ... and it
failed....but I'll have another go....

-----Original Message-----
From: Jules Bean [mailto:jules@jellybean.co.uk] 
Sent: 21 December 2007 15:33
To: Nicholls, Mark
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] nice simple problem for someone
struggling....

Nicholls, Mark wrote:
...
*instance* ShapeInterface SquareType *where*
area (SquareConstructor sideLength) = sideLength * sideLength
...
*data* SquareType a = Num a => SquareConstructor a
Now you have changed your type from SquareType to SquareType a, you need

to change the instance to:

instance ShapeInterface (SquareType a) where...

Jules