Editing John Backus (section)

==Function-level programming==
Backus later worked on a [[Function-level programming|function-level programming language]] known as [[FP (programming language)|FP]], which was described in his [[Turing Award]] lecture "Can Programming be Liberated from the [[Von Neumann programming languages|von Neumann Style]]?".<ref name="can"/> Sometimes viewed as Backus's apology for creating Fortran, this paper did less to garner interest in the FP language than to spark research into [[functional programming]] in general. When Backus publicized the function-level style of programming, his message was mostly misunderstood<ref>Hudak, Paul (1989). "Conception, Evolution, And Application Of Functional Programming Languages". ACM Computing Surveys, Vol. 21, No. 3</ref> as being the same as traditional functional programming style languages.

FP was strongly inspired by [[Kenneth E. Iverson]]'s [[APL (programming language)|APL]], even using a non-standard [[Character encoding|character set]]. An FP [[Interpreter (computing)|interpreter]] was distributed with the [[Berkeley Software Distribution|4.2BSD]] [[Unix]] operating system, but there were relatively few implementations of the language, most of which were used for educational purposes.

Backus spent the latter part of his career developing [[FL (programming language)|FL]] (from "Function Level"), a successor to FP. FL was an internal IBM research project, and development of the language stopped when the project was finished. Only a few papers documenting it remain, and the source code of the compiler described in them was not made public. FL was at odds with functional programming languages being developed in the 1980s, most of which were based on the [[lambda calculus]] and [[static typing]] systems instead of, as in APL, the concatenation of primitive operations. Many of the language's ideas have now been implemented in versions of the [[J (programming language)|J programming language]], Iverson's successor to APL.