Richard Stallman

Richard Matthew Stallman, founder of the GNU Project, was an early adopter of APL, and used it to write a text editor as a high school student in the summer of 1969. The same year, he also wrote a now famous rhyme: "Rho, rho, rho of X Always equals 1 Rho is dimension, rho rho rank. APL is fun!" This plays on the fact that  gives the shape (length of each axis; "dimension") of   while   gives the rank (number of axes/dimensions) and since the number of axes is always a count, it is a single number, which has the shape   if a vector, and   always returns a vector: