ion1

What is inside Haskell IO?

<lambdabot> shachaf says: getLine :: IO String contains a String in the same
            way that /bin/ls contains a list of files

There are multiple ways IO could be implemented internally. Here’s a demonstration of one.

MiniIO (below) implements an ADT of arbitrarily chosen primitives that represent I/O operations and a way to combine them. One can create, evaluate and manipulate MiniIO values without causing any side effects to occur. That is what example in Main.hs does. The same applies to real IO values in Haskell: you can create a big list of print "hello"s and later pick which ones to actually execute.

CyberShadow

lukaszlew

-- Based on: http://augustss.blogspot.com/2007/10/simpler-easier-in-recent-paper-simply.html
import Data.List (delete, union)
{- HLINT ignore "Eta reduce" -}

-- File mnemonics:
--   env = typing environment
--   vid = variable identifier in Bind or Var
--   br = binder variant (Lambda or Pi)
--   xyzTyp = type of xyz
--   body = body of Lambda or Pi abstraction