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Suppose that you decide to define an ordinary
function—not a member function—that takes an ordinary railroad-car
argument and computes that car's volume. You might try to define
ordinary_capacity_function as an ordinary function by having it give
all the work to the already-defined capacity virtual member
function:
// DEFECTIVE attempt to define ordinary_capacity_function!
double ordinary_capacity_function (railroad_car r) {
return r.capacity ( );
}
You might think that this function would work properly in the
analyze_train program if called as follows:
for (n = 0; n < car_count; ++n) {
// Display short name and capacity and terminate the line:
cout << train[n] -> short_name ( )
<< " "
<< ordinary_capacity_function (*train[n])
<< endl; ---------
} ^
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Dereferenced array pointer identifies --*
a chunk of memory that holds a box car,
tank car, engine, or caboose
Perhaps unexpectedly, incorporating this version of
ordinary_capacity_function into the analyze_train
program leads to the following result:
eng 0 box 0 box 0 tnk 0 cab 0