FL (programming language)

FL, short for Function Level, is a programming language created at IBM Research in Almaden, California by John Backus, John Williams and Edward Wimmers in the 1980s and documented in a 1989 report. It was designed as a successor to Backus's earlier FP language, adding specific support for what Backus called function-level programming, where whole functions rather than individual values are the main things a program combines and transforms. FL is a dynamically typed, strict functional language with throw and catch exception handling similar to ML's. Each function carries an implicit history argument, a mechanism used both for strictly functional input and output and to link FL code to routines written in C, letting a function-level program interact with the outside world and with conventional software without abandoning its functional discipline.