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Under a declarative reading, the order of rules, and of goals within rules, is irrelevant since logical disjunction and conjunction are commutative. Procedurally, however, it is often important to take into account Prolog's execution strategy, either for efficiency reasons, or due to the semantics of impure built-in predicates for which the ...
Prolog is a logic programming language that has its origins in artificial intelligence, automated theorem proving and computational linguistics. [1] [2] [3]Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is intended primarily as a declarative programming language: the program is a set of facts and rules, which define relations.
The :-symbol is read as "if", and the comma is read "and", so these rules mean: X is an ancestor of Y if X is a parent of Y. X is an ancestor of Y if X is a parent of some Z, and Z is an ancestor of Y. The meaning of a program is defined to be the set of all of the facts that can be deduced using the initial facts and the rules.
The first Prolog program, also written in 1972 and implemented in Marseille, was a French question-answering system. The use of Prolog as a practical programming language was given great momentum by the development of a compiler by David H. D. Warren in Edinburgh in 1977.
Fernando Pereira and David Warren, two other early architects of Prolog, coined the term "definite clause grammar" and created the notation for DCGs that is used in Prolog today. They gave credit for the idea to Colmerauer and Kowalski, and they note that DCGs are a special case of Colmerauer's metamorphosis grammars.
This is called a green cut operator.The ! tells the interpreter to stop looking for alternatives; however, if gotmoney(X) fails it will check the second rule. Although checking for gotmoney(X) in the second rule may appear redundant since Prolog's appearance is dependent on gotmoney(X) failing before, otherwise the second rule would not be evaluated in the first place.
In this tree, the lowest common ancestor of the nodes x and y is marked in dark green. Other common ancestors are shown in light green. In graph theory and computer science, the lowest common ancestor (LCA) (also called least common ancestor) of two nodes v and w in a tree or directed acyclic graph (DAG) T is the lowest (i.e. deepest) node that has both v and w as descendants, where we define ...
The following Comparison of Prolog implementations provides a reference for the relative feature sets and performance of different implementations of the Prolog computer programming language. A comprehensive discussion of the most significant Prolog systems is presented in an article published in the 50-years of Prolog anniversary issue of the ...