+1, I‘ve often wanted this but don’t want to add a dependency just for bool, so I end up writing it myself, locally in a where every time, which doesn't feel very Haskelly to do!

I would even like it in Prelude, but I expect that to get much more opposition so this proposal should probably not discuss that possibility at all.

On Wed, Sep 11, 2013 at 12:02 AM, Oliver Charles <ollie@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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