Re: Lisp history: IF, etc.

Julieta Shem <jshem@yaxenu.org> writes:

Paul Rubin <no.email@nospam.invalid> writes:
>

Alan Bawden <alan@csail.mit.edu> writes:

It's a common misconception that McCarthy was trying to turn Lambda
Calculus into a programming language. ...  He added LAMBDA (and LABEL)
because he needed LAMBDA in order to define recursive functions, but
as he himself often admitted, he didn't really understand Lambda
Calculus, he just needed the notation. 

>
I see, yes, and this is confirmed by his History of Lisp article.  His
Wikipedia biography also surprised me a bit.  For some reason I had
thought of him as an academic mathematical logician who later somehow
got involved with computers, but it was more like the other way around.
Thanks.

>
His PhD was in mathematics---differential equations.  He would think up
things like a simple function that is continuous but nowhere
differentiable on the real line [1].  He was a mathematician by all
accounts.  It's pretty hard to remove mathematics from computer science.
The culture seems to be that if a mathematician contributes more to the
field of computer science, he is called a computer scientist.
>
I also agree that he was a logician: he worked on a mathematical basis
for computer science.  A mathematical basis for computer science must be
classified as logic.  He was interested in proving programs were
correct.  His idea of a conditional expression is precisely to write
mathematical functions in high precision.  Mathematics in high
precision---that's a logician.
>
The creation of LISP by John McCarthy was surely not at first with
intention of a programming language.  In fact, it was Steve Russell, his
student at the time, that first had the idea of implementing EVAL and
did it.  I believe McCarthy was even somewhat surprised because, then,
he did not think of LISP having that kind of purpose.

--8<---------------cut here---------------start------------->8---
What happened next was that, some time in late 1958, Steve Russell, one
of McCarthy's grad students, looked at this definition of eval and
realized that if he translated it into machine language, the result
would be a Lisp interpreter.

This was a big surprise at the time. Here is what McCarthy said about it
later in an interview:

  Steve Russell said, look, why don't I program this eval..., and I said
  to him, ho, ho, you're confusing theory with practice, this eval is
  intended for reading, not for computing. But he went ahead and did
  it. That is, he compiled the eval in my paper into [IBM] 704 machine
  code, fixing bugs, and then advertised this as a Lisp interpreter,
  which it certainly was. So at that point Lisp had essentially the form
  that it has today.... 

Suddenly, in a matter of weeks I think, McCarthy found his theoretical
exercise transformed into an actual programming language-- and a more
powerful one than he had intended.

Source: Paul Graham's ``Revenge of the Nerds'', May 2002.
https://www.paulgraham.com/icad.html
--8<---------------cut here---------------end--------------->8---