Functions are invoked by applying them to arguments. In logic languages, a different technique is followed. Data objects are never declared. For instance, Prolog uses terms as a collection of elements to construct statements. Terms are constants, variables or integers.
Terms are to be entered into Predicates.
Predicate is also called a Structure. Functional programming languages don t use class hierarchy. In Functional programming languages, where list structure s are the primary data structure available, they use recursion to control mechanism for repeating sequences of statements. Functional programming describes all computer operations as mathematical functions on inputs. Typically, a function can be created and returned from other functions as first-class data.