APL is the first language not based on the lambda calculus that is not word-at-a-time and uses functional programming forms. Unfortunately, however, APL still splits programming into a world of expressions and a world of statements. Thus the effort to write one-line programs is partly motivated by the desire to stay in the world of expressions.
APL is a mistake, carried through to perfection. It is the language of the future for the programming techniques of the past: it creates a new generation of coding bums.
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.
APL is a write only language.