The best semantics for fexprs are probably Kernel's: a fexpr receives as parameters (1) the AST (2) the lexical environment in which the fexpr is called. (This

The best semantics for fexprs are probably Kernel's: a fexpr receives as parameters (1) the AST (2) the lexical environment in which the fexpr is called. (This dynamic lexical environment is given in addition to the captured static lexical environment - the env in which the fexpr was defined.) I believe this two-argument fexpr design goes way back, but I'm not sure. http://web.cs.wpi.edu/~jshutt/kernel.html http://web.cs.wpi.edu/~jshutt/kernel.html