MATLAB Programming

9 Classes and Objects
% SUBSREF
switch s.type
case '()'
ind = s.subs{:};
for k = 1:length(ind)
b(k) = eval(strrep(char(a),'x',['(' num2str(ind(k)) ')']));
end
otherwise
error('Specify value for x as p(x)')
end
Once the polynomial expression has been generated by the char method,
the strrep function is used to swap the passed in value for the character x.
The eval function then evaluates the expression and returns the value in
the output argument.
Note that if you perform an indexed reference from within other class
methods, MATLAB calls the built-in subsref or subsassign. See“Behavior
Within Class Methods” on page 9-15 for more information.
Overloading Arithmetic Operators for polynom
Several arithmetic operations are meaningful on polynomials and should be
implemented for the polynom class. When overloading arithmetic operators,
keep in mind what data types you want to operate on. In this section, the
plus, minus, andmtimes methods are defined for the polynom class to
handle addition, subtraction, and multiplication on polynom/polynom and
polynom/double combinations of operands.
Overloading the + Operator
If either p or q is a polynom, the expression
p + q
generates a call to a function @polynom/plus.m, if it exists (unless p or q is
an object of a higher precedence, as described in “Object Precedence” on page
9-70).
The following M-file redefines the + operator for the polynom class.
9-32