On Tue, Mar 10, 2015 at 8:07 AM, Lyndon Maydwell <maydwell@gmail.com> wrote:

This looks like a great opportunity to try out the new holes functionality:

[Prelude] λ [] == _what

<interactive>:3:7:

    Found hole ‘_what’ with type: [t0]

    Where: ‘t0’ is an ambiguous type variable

    Relevant bindings include it :: Bool (bound at <interactive>:3:1)

    In the second argument of ‘(==)’, namely ‘_what’

    In the expression: [] == _what

    In an equation for ‘it’: it = [] == _what

Looks like it defaults to [Bool]!

Correct me if I'm wrong :)

Thanks Lyndon.

But on my (debian testing) ghc I get:

Prelude> [] == _what

<interactive>:2:7: Not in scope: `_what'

[ghc 7.6.3]

And my main question is the second one :

For pedagogic purposes I want to get the error -- Whats the (family of)

related options?

 

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