On Sun, 23 Dec 2007 06:42:52 -0500, Neil Mitchell <[EMAIL PROTECTED]>
wrote:
Hi Brad,
> Experience has taught me to _never_ put class contexts on data
> definitions. Now you can't write something as simple as "Empty" - you
> have to give it a class context. This is just plain annoying.
With the class context in the BST definition, ghc gives no complaints
when
I evaluate "Empty":
In some circumstances, you need to give a type sig. For example using
Hugs:
Main> Empty
ERROR - Cannot find "show" function for:
*** Expression : Empty
*** Of type : BST a
I guess GHC has enough defaulting to display this anyway.
Sorry, forgot to mention that my BST derives Show.
You'll also have the dreaded-evil-horrid monomorhpism restriction if you
type.
empty = Empty
Thanks
Neil
More stuff for me to read about :-)
Brad
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