https://github.com/fumieval/monad-skeleton

Operational monad library
https://github.com/fumieval/monad-skeleton

haskell monads

Last synced: about 2 months ago
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Operational monad library

• Host: GitHub
• URL: https://github.com/fumieval/monad-skeleton
• Owner: fumieval
• License: bsd-3-clause
• Created: 2015-03-27T07:07:21.000Z (almost 10 years ago)
• Default Branch: master
• Last Pushed: 2021-11-30T08:13:45.000Z (about 3 years ago)
• Last Synced: 2024-10-11T21:43:30.233Z (3 months ago)
• Topics: haskell, monads
• Language: Haskell
• Homepage:
• Size: 43 KB
• Stars: 30
• Watchers: 8
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
monad-skeleton

======================

[![Build Status](https://travis-ci.org/fumieval/monad-skeleton.svg?branch=master)](https://travis-ci.org/fumieval/monad-skeleton)

[![Hackage](https://img.shields.io/hackage/v/monad-skeleton.svg)](https://hackage.haskell.org/package/monad-skeleton)

This package provides `Skeleton`, an operational monad (i.e. free monad that does not require the Functor implementation). The internal encoding

gives O(1) bind and monadic reflection.

`Skeleton` promotes unit instructions to a monad. It is isomorphic to

`MonadView (Skeleton t)`:

```haskell

data MonadView t m x where

  Return :: a -> MonadView t m a

  (:>>=) :: !(t a) -> (a -> m b) -> MonadView t m b

boned :: MonadView t (Skeleton t) a -> Skeleton t a

debone :: Skeleton t a -> MonadView t (Skeleton t) a

```

GADTs are handy to define instructions:

```haskell

data Interaction x where

  Get :: Interaction String

  Put :: String -> Interaction ()

echo :: Skeleton Interaction ()

echo = bone Get >>= bone . Put

```

Use `debone` to interpret a computation.

```haskell

interpret :: Skeleton Interaction a -> IO a

interpret m = case debone m of

  Return a -> return a

  Get :>>= k -> getLine >>= interpret . k

  Put s :>>= k -> putStrLn s >>= interpret . k

```