programming (FP) A program in a functional language consists
an expression whose value is output as the program's result.
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
The order of evaluation of subexpressions is determined by the
are evaluated before applying a function whereas in a
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,
other languages such as
Lisp have a subset which is purely
functional but also contain non-functional constructs.
(2003-03-25)