package:express
Dynamically-typed expressions involving function application and variables.
Express is a library for manipulating dynamically typed Haskell
expressions. It's like Data.Dynamic but with support for
encoding function aplication and variables.
It provides the Expr type and over a hundred functions for
building, evaluating, comparing, folding, canonicalizing and matching
Expr s. See the README and Haddock documentation for more
details.