This means that for any type 'b' you can construct a value of type 'Branch tok st a' by passing to Branch an argument of type '(PermParser tok st (b -> a))' and 'GenParser tok st b'. This also means that when you're given a value of type Branch tok st a, you don't know what that 'b' type was; the only thing you know is that the 'b' in 'b -> a' in the first argument of Branch is the same as the 'b' in 'GenParser tok st b'.
See also: the haskellwiki page on existential types. 2009/9/2 zaxis <z_a...@163.com>: > > data Branch tok st a = forall b. Branch (PermParser tok st (b -> a)) > (GenParser tok st b) > > please shed a light on me, thanks! > -- > View this message in context: > http://www.nabble.com/How-to-understand-the-%27forall%27---tp25250783p25250783.html > Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Eugene Kirpichov Web IR developer, market.yandex.ru _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
