O'Hugs

- the O'Haskell interpreter -

- Version 0.5, January 31, 2001 -

O'Hugs is an interpreter for O'Haskell built upon the popular Haskell interpreter Hugs (version 1.3b). New features in version 0.5 of O'Hugs include:

A more refined interface to Tk, including support for the optional Tk extension Tix.

Support for network programming via TCP and UDP.

Much improved library documentation.

Local universal quantification of any free type variables in a record definition. Example:
```
   struct Id = id :: a -> a
   v = (\r -> r.id r.id) {id x = x}
   
```

Local existential quantification of any free type variables in a datatype definition. Example:

   data Some = Some a (a -> Int)
   v' = map (\(Some x f) -> f x) [Some 7 (+1), Some "apa" length]

Generators of the form pat <- templ are now allowed among the state variable definitions in a template expression. Such a definition results in a new, local instance of templ being created for each instance of the enclosing template expression.

The overloading system now takes subtyping into account when resolving overloading. This means that for a contravariant class C (e.g., Eq or Show), a predicate C t is satisfied as long as there exists a unique smallest supertype of t that is an instance of C.

The fix monad syntax for defining recusive generator bindings is now supported (see the O'Haskell survey).

Several embarrassing bugs are now fixed!

Subtype constraints in type annotations are still not supported, though, and the implementation continues to be based on Hugs 1.3b (which implies just a rudimentary module system and lack of full Haskell 98 compliance).

See further the list of known bugs, and some of the planned enhancements for O'Hugs.

New library documentation

Look here!

Download O'Hugs 0.5

Full source distribution in tar-format.
Binary distribution for MacOS/PPC as a StuffIt archive (see the list of current limitations, though). See also the guide for compiling under MacOS.
Binary distribution for MS Windows in Zip format. See also the installation and build instructions for Windows.

Anonymous CVS access

To stay up-to-date with the development version of O'Hugs, you can use anonymous CVS access by the following steps:

cvs -d :pserver:anoncvs@glass.cse.ogi.edu:/cvs login

When asked for password, enter cvs.

cvs -d :pserver:anoncvs@glass.cse.ogi.edu:/cvs checkout -P ohugs

Bug reports, comments, and other suggestions should be sent to nordland@cse.ogi.edu.

Page maintained by Johan Nordlander. Last modified: January 31 2001