"Maxwell's equations of software" examined

The blog post on Ken Shirriff's website delves into the concept of the "Maxwell's Equations of Software," as quoted from Alan Kay. The post explores a half-page code snippet from the Lisp 1.5 Manual, written in 1961 by John McCarthy et al, which is considered the embodiment of Lisp itself. The code defines a universal Lisp function called evalquote, showcasing the meta-language M-expressions that can be translated into S-expressions. The code demonstrates how functions like CAR, CDR, CONS, ATOM, EQ, LAMBDA, and LABEL are implemented using a few primitives. It highlights the concept that in Lisp, code and data are interchangeable, with a concise piece of code being adequate to define a basic Lisp interpreter. The post also touches on the limitations of the presented code, such as the absence of features like arithmetic and the need for additional functions like equals and cadr. Overall, the blog post provides an insightful analysis of the foundational principles of Lisp programming and the significance of the "Maxwell's Equations of Software" analogy.