Setting large chunks of code in verbatim is ugly and complicates the use of subscripts or to set comments in a proportional type face. On the other hand, the use of TeX's math mode requires the use of additional macros to achieve proper kerning in multi-letter identifiers and to typeset application by juxtaposition. The haskell style provides environments and macros that simplify setting Haskell programs in LaTeX. While the style is specifically geared towards Haskell, it should also be useful for other functional languages.
For more detailed documentation, see the user manual.