Functional, symbolic programming language for operating on multidimensional arrays

APL (named after the book A Programming Language) is an interactive array-oriented programming language and integrated development environment, which is available from a number of commercial and noncommercial vendors and for most computer platforms


  • The initial motive for developing APL was to provide a tool for writing and teaching. Although APL has been exploited mostly in commercial programming, I continue to believe that its most important use remains to be exploited: as a simple, precise, executable notation for the teaching of a wide range of subjects.
  • There is a programming language called APL (an acronym for A Programming Language, how clever) that has more than a little Martian in it. APL was the first computer language I ever learned (on a major IBM mainframe), and when I learned it, I learned a little more than just APL.

    APL uses a very compact notation, including its very own character set, which bears little resemblance to our familiar ASCII. The character set has dozens of odd little symbols, each of which is capable of some astonishing power such as matrix inversion. You can do more in one line of APL than you can in one line of anything else I have ever learned since. The combination of the strange symbol set and the vanishingly compact notation makes it very hard to read and remember what a line of code in APL actually does.

    • Jeff Duntemann, Assembly Language Step-by-Step.
  • APL is a write only language.
    • Anonymous, widely repeated remark: Quoted in Ulf Grenander (1982) Mathematical experiments on the computer. p. 63.
  • Rho, rho, rho of X
    Always equals 1
    Rho is dimension, rho rho rank.
    APL is fun!

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