https://github.com/winterland1989/data-has

Simple extensible product
https://github.com/winterland1989/data-has

Last synced: 9 days ago
JSON representation

Simple extensible product

• Host: GitHub
• URL: https://github.com/winterland1989/data-has
• Owner: winterland1989
• License: bsd-3-clause
• Created: 2016-11-23T04:02:10.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2020-12-01T05:39:56.000Z (almost 4 years ago)
• Last Synced: 2024-04-26T05:44:52.239Z (6 months ago)
• Language: Haskell
• Size: 10.7 KB
• Stars: 38
• Watchers: 5
• Forks: 3
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG
  • License: LICENSE

Awesome Lists containing this project

README

        
data-has

========

[![Hackage](https://img.shields.io/hackage/v/data-has.svg?style=flat)](http://hackage.haskell.org/package/data-has)

[![Build Status](https://travis-ci.org/winterland1989/data-has.svg)](https://travis-ci.org/winterland1989/data-has)

A simple extensible product system, a typical usage is to free you from considering how to layer your monad stack, because your can now extend your monad in one layer:

```haskell

 {-# LANGUAGE FlexibleContexts #-}

 -- in some library code

 ...

 logInAnyReaderHasLogger :: (Has Logger r, MonadReader r m) => LogString -> m ()

 logInAnyReaderHasLogger s = asks getter >>= logWithLogger s

 queryInAnyReaderHasSQL :: (Has SqlBackEnd r, MonadReader r m) => Query -> m a

 queryInAnyReaderHasSQL q = asks getter >>= queryWithSQL q

 ...

 -- now you want to use these effects together

 ...

 logger <- initLogger  ...

 sql <- initSqlBackEnd ...

 (`runReader` (logger, sql)) $ do

       ...

       logInAnyReaderHasLogger ...

       ...

       x <- queryInAnyReaderHasSQL ...

       ...

...

```