[Infowarrior] - The Idea of Lisp

[Richard Forno]

The Idea of Lisp

Eric Normand            Dec 13, 2016

LISP. It conjures up visions of a bygone age of computers the size of refrigerators, ALL CAPS CODE, and parentheses. Oh! so many parentheses! So why is Object-Oriented Programming's creator so enamored with the idea of Lisp? And what can he mean by a programming language being an idea anyway? Should I blame my Computer Science education for not teaching it to me?

Lisp was first introduced to the world in a paper called Recursive Functions of Symbolic Expressions and Their Interpretation by Machines, Part I, written by John McCarthy. In it, McCarthy introduces many new ideas to programming. Among them are conditional expressions (that's right, if/then/else) and using more than one letter--sometimes even words and phrases--for variables (like they still do in math). Your favorite programming language owes those two features to John McCarthy. But there is an even deeper idea lurking in the definition of Lisp itself.

He defines 5 primitive operations (atom, eq, cons, car, and cdr) along with a conditional expression. It also assumes the ability to define functions. And then he uses those to define an entire programming language, defined in itself. Let me say that again: John McCarthy wrote 6 easy things in machine code, then combined them to make a programming language. Before that, the only higher-level programming language was Fortran, which took 18 man-years to develop. Fortran was a big achievement, but Lisp was a big idea.

Let's unpack this tremendous idea a bit:

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https://dev.to/ericnormand/the-idea-of-lisp

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