Re: [Haskell-cafe] [] == []

And my main question is the second one : For pedagogic purposes I want to get the error -- Whats the (family of) related options?

This feature is called "type holes" introduced by GHC 7.8.1. see https://wiki.haskell.org/GHC/Typed_holes in details. 2015-03-10 11:42 GMT+09:00 Rustom Mody :

On Tue, Mar 10, 2015 at 8:07 AM, Lyndon Maydwell 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?

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

-- 山本悠滋 twitter: @igrep Facebook: http://www.facebook.com/igrep Google+: https://plus.google.com/u/0/+YujiYamamoto_igrep