26 Mar
2004
26 Mar
'04
1:34 p.m.
In my opinion, even "advanced users" should adhere to The Haskell Report which says that (==) means equality.
Where does the report say that? As far as I can see, the closest quote is this:
The Eq class provides equality (==) and inequality (/=) methods.
(section 6.3.1). The report doesn't explicitly say anywhere that any assumptions about the properties of == are ever made.
If the Report calles (==) an equality method then (==) should implement equality for every Eq instance.
Arguably then, anything which is an instance of Monad should be a monad. And '+' should be addition. etc. etc. Haskell doesn't require any of these to be true, and similarly it doesn't require that every instance of '==' is equality. Cheers, Simon