[cracauer]

I apologize for the swipe at "toy languages". I tried using more common languages like the usual scripting crowd, but it wasn't successful, mostly for performance reasons. Python in particular is frustrating since the very own spec prevents pretty much all optimizations and you can't even call a function without stirring the heap.

I don't advocate a full type-safe language. In Common Lisp I generally don't have to declare any types. The compiler points out obvious, unavoidable type problems that it can deduct, e.g. inside a function that has some typed things such as literals. I can then add types as I like, to both variables and function interfaces, and the compiler points out more.

Another property of Common Lisp is that if you add type declarations they speed up your code if you compile with speed==high and safety==low. But you can also compile your code with safety set higher than speed. In that case a compiler like SBCL turns your declarations into runtime type assertions.

Then you run your automated tests in both modes and you have higher confidence in the code.