[Haskell-cafe] Is (==) commutative?

[Christian Sternagel]

Dear all,

with respect to formal verification of Haskell code I was wondering 
whether (==) of the Eq class is intended to be commutative (for many 
classes such requirements are informally stated in their description, 
since Eq does not have such a statement, I'm asking here). Or are there 
any known cases where commutativity of (==) is violated (due to 
strictness issues)?

cheers

chris