Alan Kay on Lisp and Fexprs.


Alan Kay on Lisp and Fexprs

Alan Kay is designer of Smalltalk. This citation is known, but not as well as it should be, and I think it deserves attention separately of many posts I wrote on fexprs.

"I could hardly believe how beautiful and wonderful the idea of LISP was. I say it this way because LISP had not only been around enough to get some honest barnacles, but worse, there were deep flaws in its logical foundations. By this, I mean that the pure language was supposed to be based on functions, but its most important components -- such as lambda expressions, quotes, and conds -- were not functions at all, and instead were called special forms. Landin and others had been able to get quotes and cons in terms of lambda by tricks that were variously clever and useful, but the flaw remained in the jewel. In the practical language things were better. There were not just EXPRs (which evaluated their arguments), but FEXPRs (which did not). My next questions was, why on Earth call it a functional language? Why not just base everything on FEXPRs and force evaluation on the receiving side when needed?

I could never get a good answer, but the question was very helpful when it came time to invent Smalltalk, because this started a line of thought that said 'take the hardest and most profound thing you need to do, make it great, an then build every easier thing out of it.'"

Alan Kay,
The Early History of Smalltalk.,
in: Bergin, Jr., T.J., and R.G. Gibson.
History of Programming Languages - II,
ACM Press, New York NY, and
Addison-Wesley Publ. Co., Reading MA 1996,
pp. 511-578

If you liked this article, you might be interested in On Pitman's 'Special forms in Lisp'.


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