Simon Guest asked: > Please could someone explain the meaning of | in this class declaration (from >Andrew's example): > > class (Ord k) => Map m k v | m -> k v where > lookupM :: m -> k -> Maybe v > > I couldn't find reference to this in any of my standard Haskell tutorials, nor the >Haskell 98 report. Any references?
It might not have become clear from the previous answers: this construction is not Haskell 98, but an extension. That's why it's not in the report. BTW: Already multi parameter type classes (such as "class (Ord k) => Map m k v where ...") ^ ^ ^ only one type variable allowed here aren't Haskell 98. All the best Christian Sievers _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe