Ken Iverson @ 100

Roger K.W. Hui

  The speed of modern computers has reached a point where, for many applications, the time required to program a problem may be a more important factor than the actual computing time. Attempts are made, therefore, to simplify the work of programming in various ways.
  K.E. Iverson, Ph.D. Thesis, §2A4 [Iverson 1954]

I had the singular good fortune to apprentice with Ken Iverson between 1989 and 2004, working on J. Ken and I worked in our homes in Toronto, I in my apartment in the High Park area and Ken in his apartment on Erskine Avenue and subsequently in the Manulife Center. The arrangement placed me uniquely under Ken’s influence. Oftentimes I found myself at Ken’s house, delivering the latest J version or working on a computer, and many times Ken would invite me to stay for lunch or dinner, explaining that “thou shalt not muzzle the ox when he treadeth out the corn”.

It is said that if you keep playing chess with a grandmaster, your skills can not help but improve. I had been in almost daily contact with the master between 1986 and 2004, and the following are a few of the things I have learned.

Farmer. Ken grew up on a farm near Camrose, Alberta, and only left to enlist in the armed forces in WWII. I believe that being a farmer left a lifelong imprint: expressing directly, favoring practicality, brooking no nonsense, …

Credit. When Ken was at Harvard a fellow student habitually stamped his papers “Copyright” or “Confidential”. Howard Aiken, head of the Comp Lab and Ken’s thesis supervisor, advised, “Don’t worry about people stealing your ideas. If they’re any good, you’d have to ram them down their throats!” [Falkoff & Iverson 1978].

Blame. Ken and I sometimes kidded each other about whose fault it was when something went wrong. He complained in jest that I as implementor had the attitude of “just tell me where to pour the concrete”. And I, in turn, complained in jest that he as designer had the attitude that he was never to blame: If it’s a mistake in the implementation, then it’s obviously my fault; and if it’s a mistake in the design, well then I should have caught it during the implementation.

Secret to Success. In January 1992, I was in the final struggles of writing my book An Implementation of J [Hui 1992], having difficulty and under time pressure. Around that time, Ken was polishing off several books and papers, seemingly effortlessly. I asked him what his secret was. His reply was, basically, “First, write 500 papers.”

Reading and Writing Carefully. In the early days I did not have direct access to Ken, and therefore read his papers carefully. Another example is Arthur Whitney’s “one page thing” [Hui 1992, Hui 2005] which was the final thing I studied (for one week) before writing the first line of source code for J. Over the years, I have benefitted enormously from such careful reading.

I later realized that Ken wrote carefully, in the expectation that what he wrote would be read carefully. It annoyed Ken to no end when accused of being “too terse”, for example as in “the J dictionary is too terse”, when “terse” means “effectively concise”.

Words. Ken was deeply interested in words, their use and their etymology. He indeed did read the dictionary, and kept a copy of the American Heritage Dictionary [AHD 1982] (along with other dictionaries) by his easy chair for ready reference. He especially encouraged me to consult the section on Indo-European roots in the back of the AHD, which makes deep and uncommon connections between words.

Many of Ken’s relatives and friends received from him the AHD as a present. I myself did not because I’d already owned one years before I met Ken. In fact, I gave him the third edition of the AHD as a present.

I think nothing I had ever done impressed Ken quite as much as when I found the word “rhematic” (meaning, pertaining to the formation of words), a word he had been searching for for some time. Thus the phrase “rhematic rules of J” made its way into the J dictionary [Hui & Iverson 1989-2004].

Politics. Unsurprisingly, Ken stood up for what he believed in. He once spent a few hours in jail after being arrested during a protest against the Vietnam War. In the same cell was Garry Wills, the historian and author.

Respect for People. Ken liked to tell the story of the stoic service agent: At an airport counter an irate traveller was berating the service agent over something or other, which the agent took with stoic forbearance. After the traveller went on his way, the next person in line told the agent, “I am amazed at how well you took that abuse.” The agent smiled thinly and replied, “Oh, the gentleman is flying to Chicago, but his luggage is going to Moscow.”

A Questioning and Flexible Mind. The flexibility of mind that Ken brought to his work was also demonstrated in his daily life. For example, it astounded me how often and how thoroughly Ken rearranged the furniture in his home. His explanation was, our needs have changed, and we rearranged our surroundings to meet those needs.

See Also

For more on the life and works of Ken Iverson, see:

•  Notation as a Tool of Thought [Iverson 1980]
Ken Iverson Quotations and Anecdotes [Hui 2005]
APL Quotations and Anecdotes [Hui 2010-2020]
Kenneth E. Iverson [Wikipedia 2016]
APL Since 1978 [Hui & Kromberg 2020]



AHD Editorial Staff, The American Heritage Dictionary of the English Language, Third Edition, Houghton Mifflin Company, 1982.
Falkoff, A.D., and K.E. Iverson, The Evolution of APL, ACM SIGPLAN Notices, volume 13, number 8, 1978-08.
•  Hui, R.K.W., An Implementation of J, Iverson Software Inc., 1992-01-27.
Hui, R.K.W., Remembering Ken Iverson, 2004-11.
•  Hui, R.K.W., Incunabulum, J Wiki Essay, 2005-10-28.
Hui, R.K.W., editor, Ken Iverson Quotations and Anecdotes, 2005-09-30.
Hui, R.K.W., editor, APL Quotations and Anecdotes, 2010-2020.
Hui, R.K.W., and K.E. Iverson, J Introduction and Dictionary, Jsoftware Inc., 1989-2004.
Hui, R.K.W., and M.J. Kromberg, APL Since 1978, Proceedings of the ACM on Programming Languages, volume 4, number HOPL, 2020-06.
Iverson, K.E., Machine Solutions of Linear Differential Equations, Ph.D. Dissertation, Harvard University, 1954-01.
Iverson, K.E., Notation as a Tool of Thought, Communications of the ACM, volume 23, number 8, 1980-08.
Wikipedia, Kenneth E. Iverson, 2016.

Substantially the same text appeared in Remembering Ken Iverson [Hui 2004].

created:  2004-11-01 00:00
updated: 2020-12-19 20:45