Lambda the Ultimate


History of Lisp (The history of LISP according to McCarthy's memory in 1978, presented at the ACM SIGPLAN History of Programming Languages Conference.)

This is such a fun paper which I couldn't find on LtU. It's about the very early history of programming (1950s and '60s), back when things we take for granted today didn't exist yet.

On taking apart complex data structures with functions like CAR and CDR:

It was immediately apparent that arbitrary subexpressions of symbolic expressions could be obtained by composing the functions that extract immediate subexpressions, and this seemed reason enough to go to an algebraic language.

On creating new data, i.e. CONS:

At some point a cons(a,d,p,t) was defined, but it was regarded as a subroutine and not as a function with a value. ... Gelernter and Gerberich noticed that cons should be a function, not just a subroutine, and that its value should be the location of the word that had been taken from the free storage list. This permitted new expressions to be constructed out of subsubexpressions by composing occurrences of cons

On inventing IF:

This led to the invention of the true conditional expression which evaluates only one of N1 and N2 according to whether M is true or false and to a desire for a programming language that would allow its use.

On how supreme laziness led to the invention of garbage collection:

Once we decided on garbage collection, its actual implementation could be postponed, because only toy examples were being done.

You might have heard this before:

S.R. Russell noticed that eval could serve as an interpreter for LISP, promptly hand coded it, and we now had a programming language with an interpreter.

And the rest is history...