[Haskell-cafe] [] == []

[Brandon Allbery]

On Mon, Mar 9, 2015 at 10:33 PM, Rustom Mody <rustompmody at gmail.com> wrote:

> My impression is that earlier
> [] == []
> used to give a type error.  Now it gives True.
>
> So
> 1. Which instance of == is being used?
> 2. Is there some option controlling this behavior?
>

The instance being used is (), and it's controlled by
-XExtendedDefaultRules.
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/interactive-evaluation.html#extended-default-rules

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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