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brew update | |
brew versions FORMULA | |
cd `brew --prefix` | |
git checkout HASH Library/Formula/FORMULA.rb # use output of "brew versions" | |
brew install FORMULA | |
brew switch FORMULA VERSION | |
git checkout -- Library/Formula/FORMULA.rb # reset formula | |
## Example: Using Subversion 1.6.17 | |
# |
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sealed trait Interact[A] | |
case class Ask(prompt: String) | |
extends Interact[String] | |
case class Tell(msg: String) | |
extends Interact[Unit] | |
trait Monad[M[_]] { | |
def pure[A](a: A): M[A] |
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{-# LANGUAGE GeneralizedNewtypeDeriving #-} | |
import Control.Monad.IO.Class | |
import Control.Monad.Trans.Class | |
import Prelude hiding (log) | |
-------------------------------------------------------------------------------- | |
-- The API for cloud files. | |
class Monad m => MonadCloud m where | |
saveFile :: Path -> Bytes -> m () |
(previous Yoneda blog) (reddit) (twitter)
Let's explore the Yoneda lemma. You don't need to be an advanced Haskeller to understand this. In fact I claim you will understand the first section fine if you're comfortable with map
/fmap
and id
.
I am not out to motivate it, but we will explore Yoneda at the level of terms and at the level of types.