[mas644]

The point he's trying to make is that Lisp lacks typing. In Lisp, code is data and data is code. This is what makes it so powerful. At the same time, the lack of certain safeguards found in ML can make it dangerous. ML was meant to give the flexibility of a language like Lisp but with stronger guarantees for safety.

However, I think it's a bit extreme to say a Lisp programmer could never be sure that their program was going to work...that's just disingenuous. Lisp is a dynamically typed language, but it is a safe language.

To contrast this with C++. In C++, if I call some third party mystery function, I'm not sure if it'll cause some side effect and corrupt my process memory. I can arbitrarily create a pointer, cast things to whatever I want, do some memcpys and memsets and bring the whole thing down. Not to say they're bad languages, I'm a C++ guy myself...but a lot of the security vulnerabilities in operating systems and major libraries/apps is due to the fact they're written in C or C++. Languages like ML and Lisp prevent that.