functional programming

programming (FP) A program in a functional language consists

of a set of (possibly recursive) function definitions and

an expression whose value is output as the program's result.

Functional languages are one kind of declarative language.

They are mostly based on the typed lambda-calculus with

constants. There are no side-effects to expression

evaluation so an expression, e.g. a function applied to

certain arguments, will always evaluate to the same value (if

its evaluation terminates). Furthermore, an expression can

always be replaced by its value without changing the overall

result (referential transparency).

The order of evaluation of subexpressions is determined by the

language's evaluation strategy. In a strict

(call-by-value) language this will specify that arguments

are evaluated before applying a function whereas in a

non-strict (call-by-name) language arguments are passed

unevaluated.

Programs written in a functional language are generally

compact and elegant, but have tended, until recently, to run

slowly and require a lot of memory.

Examples of purely functional languages are Clean, FP,

Haskell, Hope, Joy, LML, Miranda, and SML. Many

other languages such as Lisp have a subset which is purely

functional but also contain non-functional constructs.

See also lazy evaluation, reduction.

Lecture notes.

or the same in dvi-format.

FAQ.

SEL-HPC Article Archive.

(2003-03-25)