newtype | data

[Marcin 'Qrczak' Kowalczyk]

05 Oct 2001 11:53:05 -0700, Carl R. Witty <cwitty@newtonlabs.com> pisze:

> Data> (T2 undefined) `seq` ()
> *** Exception: Prelude.undefined
> Data> (T3 undefined) `seq` ()
> *** Exception: Prelude.undefined
> 
> I can't think of a semantic difference between newtype and data
> with a single unary strict constructor;

It could indeed be represented in the same way, but they behave
differently in pattern matching: case undefined of T _ -> ()
is () in the case of newtype and undefined in the case of strict data.

-- 
 __("<  Marcin Kowalczyk * qrczak@knm.org.pl http://qrczak.ids.net.pl/
 \__/
  ^^                      SYGNATURA ZASTĘPCZA
QRCZAK