Husk is a dialect of Scheme written in Haskell that implements a superset of the R⁵RS standard and a large portion of the R⁷RS-small language. Advanced features are provided including continuations, hygienic macros, libraries, and a full numeric tower.

Husk may be used as either a stand-alone interpreter or as an extension language within a larger Haskell application. By closely following the R⁵RS standard, the intent is to develop a Scheme that is as compatible as possible with other R⁵RS Schemes. Husk is mature enough for use in production applications, however it is not optimized for performance-critical applications.

Scheme is one of two main dialects of Lisp. Scheme follows a minimalist design philosophy: the core language consists of a small number of fundamental forms which may be used to implement other built-in forms. Scheme is an excellent language for writing small, elegant programs, and may also be used to write scripts or embed scripting functionality within a larger application.

More information is available on the husk website.

Installation

1. Prerequisites: You will need the Haskell Platform if you don't already have a recent copy installed.

2. Install Husk using cabal:

    cabal update
    cabal install husk-scheme
   

   If you are new to Haskell or just want to run Husk you may also need to run:

    cabal install --lib husk-scheme
   

3. Adjust your PATH: Before running Husk you may also need to add the cabal executable directory to your path. On Linux this is ~/.cabal/bin.

4. Now you are ready to start up the interpreter:

    justin@my-pc$ huski
      _               _        __                 _                          
     | |             | |       \\\               | |                         
     | |__  _   _ ___| | __     \\\      ___  ___| |__   ___ _ __ ___   ___  
     | '_ \| | | / __| |/ /    //\\\    / __|/ __| '_ \ / _ \ '_ ` _ \ / _ \ 
     | | | | |_| \__ \   <    /// \\\   \__ \ (__| | | |  __/ | | | | |  __/ 
     |_| |_|\__,_|___/_|\_\  ///   \\\  |___/\___|_| |_|\___|_| |_| |_|\___| 
                                                                         
     http://justinethier.github.com/husk-scheme                              
     (c) 2010-2014 Justin Ethier                                             
     Version 3.18 
                                                                         
    huski> (define (hello) 'world)
    (lambda () ...)
    huski> (hello)
    world
   

Husk has been tested on Windows, Linux, and FreeBSD.

Documentation

The online user manual provides an overview of the Scheme language as implemented by Husk, including:

• A getting started guide.
• Instructions for using the Haskell API
• An alphabetical listing of the Scheme API.

Directory Structure

• docs - Documentation has been moved from here to the gh-pages branch.
• examples - Example programs, mostly written in Scheme.
• extensions - Haskell-based extensions to Husk.
• hs-src - Haskell source code for Husk.
• lib - Library portions of Husk written in Scheme.
• scripts - Build scripts for Husk and a basic Emacs integration script.
• tests - Functional tests for Husk. These can be run automatically by using make test from the main Husk directory.

License

Copyright (C) 2010 Justin Ethier

Husk scheme is available under the MIT license.

The interpreter is based on code from the book Write Yourself a Scheme in 48 Hours written by Jonathan Tang and hosted / maintained by Wikibooks.