Declarative programming in PROLOG

The declarative programming by declarative languages is clearly the best option a programmer can have for a completely readable, flexible and extensible code. Today, the economics of programming is clearly focused on the declarative paradigm while most imperative languages are trying to become cost effective by using new added declarative features for productivity and ease of use, like the Java 8. This paper tries to demonstrate a declarative language like PROLOG is perfectly suitable to be used to solve even common programming issue, like deciding an element is part of an array or not