Re: [Haskell-cafe] What does the Haskell type system do with "show (1+2)"?

On Thu, 12 Jan 2006 Jeff.Harper@handheld.com wrote:

What does the Haskell type system do with expressions such as these . . . ? show 1 show (1+2)

The type of the subexpressions "1" and "1+2" are "ambiguous" since they have type "(Num a) => a". I'm under the assumption before "1+2" is evaluated, the "1" and "2" must be coerced into a "concrete" type such as Int, Integer, Double, etc, and before "show 1" is evaluated, the "1" must be coerced into a "concrete" type. Is my assumption correct?

Yep. If you start ghc with -Wall option then it also tells you that some automatism is invoked.