> As for LISP, TypeScript services as a good test case for layering dynamic languages with type systems, so why not TypeLISP? Lisp users think that a 'dynamica

> As for LISP, TypeScript services as a good test case for layering dynamic languages with type systems, so why not TypeLISP? Lisp users think that a 'dynamical' and a 'dynamically typed' language are two different things. Lisp is both. Being 'dynamically typed' supports or simplifies a lot of dynamical features. There are a bunch of languages which implement a subset of Lisp features and which were adding type systems. Historically much of typed FP was developed out of Lisp tradition. Common Lisp for example has CLOS definitions like: (defclass person (living-thing) ((name :type string))) So the definition makes clear that are a class/type which inherits from the class/type living-thing. It also defines that contents of the slot name are of type string. A CLOS method then is: (defmethod say ((from person) (to person) (m message)) ...) Which means that an object of class person sends to another object of class person an object of class message. Multi-methods in CLOS allow us to define and dispatch on the class of several arguments. Common Lisp then also has type declarations: (defun collide (a b) (declare (type moving-object a b)) ... ) This allows programs to document types, compilers to use types for optimization purposes and some compilers to do type checking. What Common Lisp lacks is a more extensive/expressive type system which would be competitive with what Haskell/or similar would offer.