This chapter describes how the function operator()(int,int) works for the different matrix types. Basically, for all matrix types, the function operator()(int,int) returns a reference to an element of the matrix. This reference can be used as a right-side value, like this:

x = A(i,j);

or as a left-side value (lvalue), like this:

A(i,j) = x;

What C++ data type does operator()(int,int) return? We consider only the double precision matrix types in the following sections; the rest work exactly the same way.