The Home of Haggis

Contents

• Features
• Downloading
• Installing
• Examples
• Documentation
• Papers
• Reporting bugs
• Version history
• Author
• Other links

• Multi-threaded, concurrent user interface framework.
  
  To help in structuring the interaction with the user and the outside world, Haggis uses concurrency to separate concerns. To be precise, Haggis is built on top of the concurrent extensions to the Glasgow Haskell Compiler (aka. Concurrent Haskell). The concurrency is simulated, i.e., the GHC runtime system performs pre-emptive scheduling between a collection of concurrently running state threads.

• An extensible framework for building user interfaces.
  
  Haggis offers a simple framework for building user interfaces from parts. Using only a few primitive abstractions and combinators for glueing `components' together, complete applications or new user interface abstractions can be built. Indeed, one of the goals behind Haggis is to try and eradicate the boundary between building user interface abstractions (`widgets') and writing applications.

• An (almost) complete set of common user interface abstractions.
  
  Using the Haggis core set of combinators, a large collection of user interface abstractions has been built. In scope, this collection is equal (if not bigger) to what toolkits such as Tk, Athena, Java's AWT or Fudgets (the `standard' FP toolkit) offers.

  A caveat to this (bold) claim is that the set of abstractions for handling text input and output is somewhat lacking at the moment, as there is no support for multi-line text editing or a proper abstraction for viewing large chunks of text. Expect this to change though.

• A simple model of structured graphics.
  
  To describe graphical output, Haggis opt for a non-procedural approach. Instead of viewing graphics as a sequence of side-effecting operations on some drawing surface, a simple model of structured, declarative graphics is used. A picture is described by an abstract value that can be manipulated and combined together with other picture values to compose complete graphical scenes. These picture values can then be converted into actual graphical output on the screen, or can be printed out as PostScript.

  In the cases where the graphical output have no apparent or simple compositional structure, Haggis provides also a procedural drawing interface.

  Haggis currently groks XBM, XPM and P[B,P]M image formats.

• An abstract view of the underlying window system.
  
  To try and save the user from having to learn about Haggis and the details of the underlying window system (the X Window system), Haggis tries to hide its current X11 parentage by providing some (we hope!) window system independent interfaces for accessing and communicating with the window system.

  (If you really want to see what's under the bonnet and deal with the window system more directly, you can.)

• Uses modern functional I/O model.
  
  Haggis uses the now standard Haskell way of expressing I/O, the IO monad. Interacting with the user interface components is presented as interaction with any other device, like a file or channel.

• A reasonably complete set of documentation describing the system.

Host: ftp.dcs.gla.ac.uk

Directory: pub/haskell/glasgow/

Filename: haggis-0.1c.tar.gz

Or just click one of these (binary bundles to follow):

• the compressed (.gz) Haggis source+docs tar file.
• 0.1b-0.1c compressed (.gz) diffs, see README-diffs for instructions of how to apply patches.

• Hello, World
• Haggis Counter document explaining the basic features of Haggis by a step-by-step description of a Haggis implementation of the ubiquitous counter example.
• GUIFest Counter
• 15 puzzle
• Colour mixer

• Haggis Manual
• Haggis tutorial (early version)

• Composing User Interfaces with Haggis. Sigbjorn Finne and Simon Peyton Jones
  To be presented at the 1996 Summer school on advanced Functional programming, Olympia, WA, Aug 25-30 1996.
• Concurrent Haskell Simon Peyton Jones, Andrew Gordon and Sigbjorn Finne,
  Proceedings of the ACM Symposium on Principles of Programming Languages,St Petersburg Beach, Florida, January 1996.
• Composing Haggis Sigbjorn Finne and Simon Peyton Jones.
  Proceedings of the Fifth Eurographics Workshop on Programming Paradigms for Computer Graphics, Maastricht, September 1995, Springer Verlag. (Gives an overview of the ideas behind Haggis and although some of the details of the programming model have changed since the paper was written, the basic principles still hold true.)
• Pictures: A Simple Structured Graphics Model Paper describing the simple model for doing structured graphics in Haggis. Presented at the 1995 Glasgow Workshop on Functional Programming, Ullapool.

A list of known bugs and problems can be found here.

Version History

• Glasgow Functional Programming Group
• Glasgow Haskell Compiler
• The Fudgets system.
• The Haggis files