GoKawiilA Letter from Dijkstra on APL
Roger K.W. Hui
Acknowledgments. I would like to thank Bob Bernecky, Nicolas Delcros, Jay Foad, and Eric Iverson for comments on the manuscript.
Nick Nickolov brought to my attention comments by Dijkstra on APL [0] that I had not seen before. I contacted the author of the website and obtained a copy of Dijkstra’s letter, transcribed below:
Burroughs PROF DR EDSGER W DIJKSTRA PLATAANSTRAAT 5 RESEARCH FELLOW 5671 AL NUENEN THE NETHERLANDS Dr A.Caplin
[street address]
CROYDON , Surrey
United Kingdom Tuesday 12 January 1982 Dear Dr Caplin, thank [sic] you for your letter dated 31 May (?) 1981. You were right in your reference to an APL “cult”: some adore it and others abhor it with very few in between. Allow me to offer you another explanation for that phenomenon. I think that most people (be it subconsciously) realize that “ease of use” is not the most significant aspect. Experience has show that, provided people are sufficiently thrilled by a gadget, they are willing to put up with the most terrible interfaces. Much more important is that the tool shapes the one who trains himself in its usage, just as the words we use shape our thoughts and the instrument forms the violinist. I think that a major reason for shunning APL is that many people are repelled by the influence APL has on its devotees. They implement the prayer “Dear Lord, don’t let me become like them” by ignoring it. A typical characteristic of the APL devotee is, for instance, his closeness to an implementation of it. I know of a visiting professor at an American University [sic] who, trying to teach APL, bitterly complained about the absence of APL terminals. He was clearly unable to teach it without them. And you, too, write to me that you would like to meet me in your part of the world, so that you can “demonstrate APL” to me. This is in sharp contrast to people who prefer programming languages that can be adadequately [sic] “demonstrated”—i.e. shown, taught and discussed—with pencil and paper. The fact that the printed or written word is apparently not the proper medium for the propagation of APL may offer a further explanation for its relative isolation; at the same time that fact may be viewed as one of its major shortcomings. Your writings made me wonder in which discipline you got your doctor’s degree. With my greetings and best wishes, yours ever,
(signed) Edsger W. Dijkstra PS. I apologize for the quality of my signature; having broken my right arm I have to sign with my left hand. EWD
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