Why isn't there is a map class? Sometimes you want to map a tree, or--to use the Parser Combinators document as an example--an environment. Why must one define a maptree function, a mapenvironment function, etc.? Wouldn't it be nice for there to be a map class? I figure that this idea of expanding the classes in the StdEnv applies to more than just map. Should StdEnv be expanded like that? -Nick