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Title: Happstack  
Author: World Heritage Encyclopedia
Language: English
Subject: Snap (web framework), AppJet, ColdSpring Framework, Knockout (web framework), Apache Shale
Collection: Free Software Programmed in Haskell, Free Web Server Software
Publisher: World Heritage Encyclopedia


Original author(s) Alex Jacobson
Stable release 7.0 / March 29, 2012 (2012-03-29)
Development status Beta
Operating system Portable (requires GHC and libraries)
Platform Portable
Available in Haskell
Type Application server
License BSD-3

Happstack (Haskell Application Stack) is a free application server for websites written in the functional programming language Haskell. It integrates handling Web, persistence, XML/XSLT, and templating functionality.[1]

It makes use of a number of Haskell libraries and systems such as Parsec, Cabal, Template Haskell, and monad transformers ("Your app then is just a set of state transformer functions (in the MACID Monad) that take an event and state as input and that evaluate to a new state, a response, and a (possibly null) set of sideeffects."[1]) among others.


  • Relation to HAppS 1
  • See also 2
  • References 3
  • External links 4

Relation to HAppS

Happstack is the continuation of the HAppS project.[2] The project name was changed to highlight the transition to a more open development model and a change in project leadership. The transition was made with the blessing of Alex Jacobson, and the HAppS developers are still involved in the coding.

See also


  1. ^ a b "4.10.1 HAppS – Haskell Application Server"
  2. ^ Happstack FAQ

External links

  • Happstack Maintained, current version
  • HAppS homepage
  • Author of HAppS Alex Jacobson presenting HAppS to the Bay Area Functional Programmers group (video & slides)
  • Haskell Application Server - HAppS
  • "Case Study: Using Haskell and HAppS for Openomy API v2.0"
  • Self-Demoing Cabal Installable HAppS Tutorial
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