13.12.txt

Exercise 13.12: How many destructor calls occur in the following code fragment?

	bool fcn(const Sales_data *trans, Sales_data accum)
	{
		Sales_data item1(*trans), item2(accum);
		return item1.isbn() != item2.isbn();
	}

A destructor call occurs every time a class object is destroyed. trans and
accum are temporary copies.  They are destroyed when they fall out of scope at
the end of the code. trans, however, does not invoke a destructor because it is
a built-in type. item1 and item2 are local class objects. They, too, are
destroyed when they fall out of scope. Like, accum, a call to thej destructor
occurs when the are destroyed. The order of their destruction is the inverse of
their construction: item2, item1, accum. Each object has a string member.
Therefore, Sales_data destructor calls the string destructor to handle the
deletion.  Thus, in total, 6 destructor calls are made: 3 Sales_data destructor
calls and 3 string destructor calls.

By Faisal Saadatmand