Glossary

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F

Index


Fact

Context

A term in Prolog.

Definition

A fact is a head followed by a period.

Thus the syntax of a fact is as follows:

head.

A fact is a kind of (or a subtype of) clause.


Formal parameter

Context

A term in programming language theory, as well as CG theory.

Conceptual graphs

Definition

A parameter to a lambda expression can either be a formal parameter or an actual parameter.

A formal parameter to a lambda expression is a concept in the lambda expression whose referent is a lambda.

CG example

For example, in the following usage of a lambda expression:

  [Man: Socrates]<-([Man: ]->(Attr)->[Mortal])

"[Man: ]" is the formal parameter which is replaced by the actual parameter "[Man: Socrates]" when the lambda expression is used.

We see, then, that "formal parameter" is complementary to actual parameter.

Prolog+CG

Definition

In Prolog+CG, a predicate may have zero or more formal parameters. The formal parameters are the terms in parentheses after the functor in the definition of the predicate.

Prolog+CG Example

Consider the following Prolog+CG program:


student(Elisa, 2003).

enrolled_in_year(S,Y) :- student(S,Y).

Here, the formal parameters of the "enrolled_in_year" predicate "S" and "Y".

Likewise, the formal parameters of the "student" predicate are "Elisa" and "2003".

In contrast, the actual parameters of the "student" predicate in the body of the rule for "enrolled_in_year" are "S" and "Y".


Free variable

Context

A term in Prolog.

Definition

A free variable is a variable which has not been bound to a value, i.e., which has not been given a value.


Functor

Context

A term in Prolog.

Definition

A functor is the name of a structure. It must be an identifier.


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