I met Roger briefly as a presentation on J at SFSU. He seemed like a mellow, straightforward person and I enjoyed how he explained a one-page long set of c-mac

I met Roger briefly as a presentation on J at SFSU. He seemed like a mellow, straightforward person and I enjoyed how he explained a one-page long set of c-macros that expanded into the initial J compiler (written by Ken Iverson or someone else). I remember asking him, "How do you debug something like that" and he said "don't make mistakes".