[Haskell-cafe] Prolog-style patterns
roma at ro-che.info
Tue Apr 9 16:43:07 CEST 2013
* Malcolm Wallace <malcolm.wallace at me.com> [2013-04-09 15:34:01+0100]
> On 9 Apr 2013, at 14:46, Sturdy, Ian wrote:
> > As far as the use of Eq goes, Eq is already enshrined in pattern matching by pattern matching against literals.
> Not true. Pattern-matching literals explicitly avoids any use of Eq. Demonstration:
> data Foo = Foo | Bar
> instance Eq Foo where
> _ == _ = True
> isFoo Foo = True
> isFoo Bar = False
> main = do print (isFoo Bar)
> print (Foo==Bar)
I think he meant numeric literals.
More information about the Haskell-Cafe