Hugs (Haskell User's Gofer System) (also Hugs 98) is a bytecode interpreter for the functional programming language Haskell. Hugs is the successor to Gofer, and was originally derived from Gofer version 2.30b.It offers fast compilation of programs and reasonable execution speed. It also comes with a simple graphics library. Hugs is good for people learning the basics of Haskell, but is by no means a "toy" implementation. It is the most portable and lightweight of the Haskell implementations.
Hugs deviates from the Haskell 98 specification in several minor ways. For example, Hugs does not support mutually recursive modules. The Hugs prompt accepts expressions for evaluation, but not module, type or function definitions.