Proposal: Data.Bool.implies

[David Feuer]

-1. We already have a `<=` operator.

On Sun, Jan 17, 2016 at 9:17 PM, Niklas Hambüchen <mail at nh2.me> wrote:
> I propose to add to Data.Bool:
>
>     -- | Boolean implication.
>     implies :: Bool -> Bool -> Bool
>     implies True  x = x
>     implies False _ = True
>
>     infix 4 `implies` -- same as (==)
>
> The request for this is quite old (see e.g.
> http://neilmitchell.blogspot.de/2007/02/logical-implication-in-haskell.html).
>
> I believe that by not trying to use an operator for it, and keeping it
> in Data.Bool, we can avoid doing anything wrong.
>
> A quick superficial search on Stackage Hoogle suggests that adding this
> function should create no breakage (4 packages define their own function
> called `implies`, none of them import Data.Bool).
>
> `infix` instead of `infixl` or `infixr` to force you to bracket it; for
> the same reason it has the same precedence as `==`.
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