Lisp History July 12th, 2009
Patrick Stein

To make sure that I’m extra prepared for my upcoming talk on Lisp Macros, I’ve been scouring the net reading everything I can find that other folks have written about macros.

This set of lecture notes is a really nice explanation of basic Lisp macros and the whole backquote/comma paradigm. I think it’s off base with its Lisp history though.

It says:

In the late 1950’s, John McCarthy invented Lisp to cover many common weaknesses of languages such as FORTRAN, COBOL and ALGOL. Thus, Lisp was the first language to truly embrace concepts such as recursion, first-class treatment of functions (i.e. they are treated just like any other data), weak typing, and macros.

Maybe I am way off base, but my understanding was that McCarthy made Lisp because FORTRAN was useful for computation and nigh impossible for proving anything. Turing machines were useful for proving things and nigh impossible for computation. My understanding was that Lisp was created to be something easier to compute in than a Turing machine yet easier to prove things in than the other languages at the time. My understanding was that Lisp macros came around three or four years later.

I suppose it’s arguable that not being able to prove things in it is a common weakness in programming languages. Heck, you’d be hard pressed to prove anything about Common Lisp without restricting yourself to a ridiculously small subset, and Lisp is way better off than Ruby, Python, Java, C, C#, C++, etc. I suppose it’s also arguable that the lecture notes don’t claim that McCarthy invented Lisp with macros in situ, but rather that Lisp embraced them quickly.

Me, I think it was kind of an accident. The very same things that made it easy to prove things about Lisp programs also made it easy to graft in macros. The functional nature, played out in s-expressions, is suited for macros in a way that infix languages will never be.