A functional programming system
Edit By BS Editor: Hugs 98 is a functional programming system based on Haskell 98, the de Facto standard for non-strict functional programming languages. Hugs 98 provides an almost complete implementation of Haskell 98, including:

* Lazy evaluation, higher order functions, and pattern matching.
* A wide range of built-in types, from characters to bignums, and lists to functions, with comprehensive facilities for defining new datatypes and type synonyms.
* An advanced polymorphic type system with type and constructor class overloading.
* All of the features of the Haskell 98 expression and pattern syntax including lambda, case, conditional and let expressions, list comprehensions, do-notation, OperaTor sections, and wildcard, irrefutable and `as patterns.
* An implementation of the Haskell 98 primitives for monadic I/O, with support for simple interactive programs, access to text files, handle-based I/O, and exception handling.
* An almost complete implementation of the Haskell module system. Hugs 98 also supports a number of advanced and experimental extensions including multi-parameter classes, extensible records, rank-2 polymorphism, existentials, scoped type variables, and restricted type synonyms. you can free download Hugs 98 2006 now.