Some CL implementations (including SBCL) have optional static type checking around function boundaries. Barring that, Julia is a lispy language with great supp

Some CL implementations (including SBCL) have optional static type checking around function boundaries. Barring that, Julia is a lispy language with great support for optional typing. Both of the above will get a potentially better performance when you add types (the checks are (mostly?) done at compile time). Racket also has optional types, but I think these contracts are checked at runtime? I am not sure.