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and is read as "Head is true if Body is true". A rule's body consists of calls to predicates, which are called the rule's goals. The built-in predicate,/2 (meaning a 2-arity operator with name ,) denotes conjunction of goals, and ;/2 denotes disjunction. Conjunctions and disjunctions can only appear in the body, not in the head of a rule.
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.
A rule is called ground if all of its atoms (head and body) are ground. A ground rule R 1 is a ground instance of another rule R 2 if R 1 is the result of a substitution of constants for all the variables in R 2. The Herbrand base of a Datalog program is the set of all ground atoms that can be made with the constants appearing in the program.
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 ...
In all of these languages, rules are written in the form of clauses: A :- B 1, ..., B n. and are read as declarative sentences in logical form: A if B 1 and ... and B n. A is called the head of the rule, B 1, ..., B n is called the body, and the B i are called literals or conditions. When n = 0, the rule is called a fact and is written in the ...
λProlog, also written lambda Prolog, is a logic programming language featuring polymorphic typing, modular programming, and higher-order programming.These extensions to Prolog are derived from the higher-order hereditary Harrop formulas used to justify the foundations of λProlog.
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.
Languages are categorized under the ancestor language with the strongest influence. Those ancestor languages are listed in alphabetic order. Any such categorization has a large arbitrary element, since programming languages often incorporate major ideas from multiple sources.