# get-role-cardinality [*Function*]

## Purpose

The **get-role-cardinality** function returns the number of fillers of a given role on a given concept or instance, providing that the maximum and minimum number of such fillers is the same.

## Syntax

**get-role-cardinality** *conceptOrInstance* *relation*

## Arguments

The *conceptOrInstance* argument is a Loom concept or instance.
The *relation* argument is the relation whose upper and lower bounds are to be compared.

## Value

The **get-role-min-cardinality** function returns the minimum number retriction that applies to *conceptOrInstance* for *relation*, if that minimum is the same as the maximum. Otherwise, it returns **nil**.

## Examples

(defconcept B
:is (:and (:all r A) (:exactly 3 r) (:filled-by r Joe Fred)))
(defconcept C
:is-primitive B
:implies (:and (:some s A) (:at-most 2 s))
:defaults (:filled-by s Sue))
(tellm (C Mary))
(get-role-cardinality (fc C) (fr r)) ==> 3
(get-role-cardinality (fc C) (fr s)) ==> NIL
(get-role-cardinality (fi Mary) (fr r)) ==> 3
(get-role-cardinality (fi Mary) (fr s)) ==> NIL

## See Also

Last modified: Jun 1 1995