Proposal: Add bool to Data.Bool

[Edward Kmett]

I'm +1 for bool, but find cond doesn't hit the Fairbairn threshold for me.

-Edward

On Sep 11, 2013, at 6:18 PM, Conal Elliott <conal at conal.net> wrote:

> +1 for bool
> 
> +1/2 for cond but with its signature generalized to Applicative:
> 
> > cond :: Applicative f => f a -> f a -> f Bool -> f a
> > cond = liftA3 bool
> 
> -- Conal
> 
> 
> On Tue, Sep 10, 2013 at 5:17 PM, Dan Burton <danburton.email at gmail.com> wrote:
>> +1 for Data.Bool.bool :: a -> a -> Bool -> a. It doesn't seem very important but it does add symmetry with maybe and either, and is mostly harmless residing in Data.Bool as long as it is not re-exported by Prelude.
>> 
>> On a tangent... as usual, the Applicative instance of (a ->) comes in handy for pointless programming:
>> 
>>     cond = liftA3 bool :: (a -> b) -> (a -> b) -> (a -> Bool) -> a -> b
>> 
>> 
>> -- Dan Burton
>> 
>> 
>> On Tue, Sep 10, 2013 at 4:01 PM, Christopher Done <chrisdone at gmail.com> wrote:
>>> FWIW I've added this to data-extra http://chrisdone.com/data-extra/Data-Bool-Extra.html for the meanwhile.
>>> 
>>> 
>>> On 11 September 2013 00:02, Oliver Charles <ollie at ocharles.org.uk> wrote:
>>>> Hello,
>>>> 
>>>> I would like to propose that the following is added to Data.Bool in base:
>>>> 
>>>> bool :: a -> a -> Bool -> a
>>>> bool f _ False = f
>>>> bool _ t True  = t
>>>> 
>>>> (Aka, bool f t b = if b then t else f)
>>>> 
>>>> The purpose of this is hopefully evident from its definition. I find
>>>> myself reaching for this in cases similar to where I would use 'maybe' -
>>>> often when I'm working with 'fmap' and don't want to start introducing
>>>> names for the function I am using to map over some functor.
>>>> 
>>>> I suggested this in #haskell and other people also seem frustrated this
>>>> doesn't exist, and would like to see it happen - hopefully they will
>>>> voice their support as a reply here.
>>>> 
>>>> A quick search on FPComplete's Hoogle [1] shows five equivalent
>>>> functions on the first page - and I'm sure there are more on subsequent
>>>> pages.
>>>> 
>>>> Thoughts?
>>>> - ocharles
>>>> 
>>>> ---
>>>> [1]:
>>>> https://www.fpcomplete.com/hoogle?q=Bool+-%3E+a+-%3E+a+-%3E+a&env=ghc-7.4.2-stable-13.09
>>>> 
>>>> 
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