[Haskell-beginners] Change in type that I don't understand

[Daniel Trstenjak]

On Fri, Jan 27, 2017 at 08:35:08AM -0500, David McBride wrote:
> If you have the Monomorphism restriction set, it will choose types
> based on the type defaulting rules (Num changes to Integer).  This is
> because polymorphic code is slower than code that has concrete types.

But why didn't the defaulting rules have been applied for both: 'f' and 'g'?

Greetings,
Daniel