FP (short for Functional P programming) is a programming language created by John Backus to support the Function-level programming paradigm.
Overview
The values that FP programs map into one another comprise a set which is closed under sequence formation:
if x1,...,xn are values, then the sequence <x1,...,xn> is also a value
These values can be built from any set of atoms: booleans, integers, reals, characters, etc.
FP programs are functions f that each map a single value x into another:
f:x represents the value that results from applying the function f to the value x
Functions are either primitive (i.e., provided with the FP environment) or are built from the primitives by program-forming operations (also called functionals). One such operation is constant, which transforms a value x into the constant-valued function x̄ where:
constant x̄ where x̄:y = x
for all values y (except the undefined value, which all functions, being strict, map into itself). Next there are the three principal functionals of FP:
composition f&#x°g where f&#x°g:x = f:(g:x)
construction [f1,...fn] where [f1,...fn]:x = < f1:x,...,fn:x >