Those are not demonstrations of the defaulting rules in action though. As far as I know, :t is agnostic to those and will keep showing the original polymorphic version, since you're not in a context where GHC has to sacrifice the polymorphic type and commit to a monomorphic one using a default, like when expressions are evaluated. Also I think that's effective just for the REPL (it uses extended defaulting rules that are more lax) and is done for convenience. If it was during a GHC build, you'd get loud warning when something is defaulted. Try `reverse []` for fun vs. `:t reverse []`. On Sep 29, 2016 7:48 PM, "Lai Boon Hui" wrote:

Hi, i read that the default type for Num is Integer. If we specify a type for one of the arguments: :t (1 + 1::Double) is Double

If we don't, i expect the default type for Num to come into play: However :t (1 + 1) is Num a => a

Why is that so?

-- Best Regards, Boon Hui

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