pjrt

{-# LANGUAGE GADTs, ConstraintKinds, FlexibleInstances, RankNTypes #-}

-- Our typeclass with a simple foo :: a -> String func
class Foo a where
    foo :: a -> String

-- Our test data types and their instances of Foo
data MyFoo = MyFoo String
data MyBar = MyBar Int

seanf

# Save this file (after modifying ID_VENDOR and ID_MODEL if necessary) as /etc/udev/rules.d/81-thinkpad-dock.rules

# These values seem to work for "ThinkPad Mini Dock Plus Series 3"
SUBSYSTEM=="usb", ACTION=="add|remove", ENV{ID_VENDOR}=="17ef", ENV{ID_MODEL}=="100a", RUN+="/etc/sbin/thinkpad-dock.sh"

malcolmgreaves

Main Point

Idea for a Scala macro to make working with tagged types more ergonomic.

Explanation

As a user, I want to define two variables:

• $TYPE : The name of the new type that we are creating.
• $CONTENT : The actual, underlying content of the new type.

This will define a new type called $TYPE that is a transparent, no-overhead wrapper around a value of type $CONTENT.

pjrt

{-# LANGUAGE FlexibleInstances, UndecidableInstances #-}
{-# LANGUAGE FunctionalDependencies, TypeApplications #-}

import Data.Proxy

data User

class MyClass a b | b -> a

instance MyClass Char Int