"Functional Programming: What It's All About
Functional Programming emphasizes the evaluation of expressions
rather than the execution of commands. Tracing back to calculus
mathematics, the main goal of Functional Programming is to prevent
the inadvertent changing of already calculated values. As
developers know, the most likely cause of accidental variable
modifications are functions that have access to global objects. The
reason accessing of global variables by multiple functions is
inherently dangerous is that changing a global variable in part of
a program can have unexpected effects in another part. Functional
programming isn't a replacement for Object-Oriented and
Pricedural/Imperative styles; each has a place in Web development.
Examples of Functional Programming languages include Scheme, Erlang
"Higher Order Functions
A function becomes a Higher Order function when it treats other
programming because functions are actually a Function object type.
Observe the following two functions:"