Re: [Haskell-cafe] Ambiguous type variable

wrote:

-- Given a definition of view which is essentially a synonym for show:

class View a where view :: a -> String

instance View Int where view = show

-- why does "show 2" compile, while "view 2" gives an -- 'Ambiguous type variable' error

fine = view (2::Int) noProblem = show 2 ambiguousTypeVariable = view 2

On 2010 Oct 16, at 01:25, Daniel Fischer wrote:

http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-790004.3...

Defaulting only takes place when all involved classes are defined in the Prelude or the standard libraries.

Your View class isn't, hence there's no defaulting.

Bingo. Thank you.