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

[Nicholls, Mark]

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 at jellybean.co.uk] 
Sent: 21 December 2007 15:33
To: Nicholls, Mark
Cc: haskell-cafe at 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