Beyond physics, his research interests included quantum chemistry, programming language design, cellular automata, and flexagons.
[1] After leaving Brandeis, McIntosh worked at the Aberdeen Proving Ground, and then in the Research Institute for Advanced Studies in Baltimore.
He started in the center for research and advanced studies of the Instituto Politécnico Nacional, which eventually became CINVESTAV; he worked there on the design of the CONVERT programming language.
Here, as well as the development of programming languages and software for scientific visualization, his interests returned to physics, including issues of degeneracy in the solution of physical equations, and quantum two-body problems involving a magnetic monopole (the so-called MICZ Kepler system, in which the M stands for McIntosh).
[1] After nine years at the Instituto Politécnico Nacional, McIntosh moved in 1975 to the Institute of Sciences of the Meritorious Autonomous University of Puebla, where he became the founding director of the Department of Microcomputer Applications.