MATLAB Programming

9 Classes and Objects
Object Precedence
Object precedence is a means to resolve the question of which of possibly
many versions of an operator or function to call in a given situation. Object
precedence enables you to control the behavior of expressions containing
different classes of objects. For example, consider the expression
objectA + objectB
Ordinarily, MATLAB assumes that the objects have equal precedence and
calls the method associated with the leftmost object. However, there are
two exceptions:
• User-defined classes have precedence over MATLAB built-in classes.
• User-defined classes can specify their relative precedence with respect to
other user-defined classes using the inferiorto and superiorto functions.
Forexample,inthesection“Example — A Polynomial Class” on page 9-26
the polynom class defines a plus method that enables addition of polynom
objects. Given the polynom object p
p = polynom([1 0 -2 -5])
p =
x^3-2*x-5
The expression,
1 + p
ans =
x^3-2*x-4
calls the polynom plus method (which converts the double, 1, to a polynom
object, and then adds it to p). The user-defined polynom class has precedence
over the MATLAB double class.
Specifying Precedence of User-Defined Classes
You can specify the relative precedence of user-defined classes by calling the
inferiorto or superiorto function in the class constructor.
9-70