Program Notes

Note that when a constructor has a single argument, you can use the following form when initializing a class object:

// a syntax for initializing a class object when
// using a constructor with one argument
Stonewt incognito = 275;

This is equivalent to the other two forms shown earlier:

// standard syntax forms for initializing class objects
Stonewt incognito(275);
Stonewt incognito = Stonewt(275);

However, the last two forms can also be used with constructors that have multiple arguments.

Next, note the following two assignments from Listing 11.18:

incognito = 276.8;
taft = 325;

The first of these assignments uses the constructor with a type double argument to convert 276.8 to a type Stonewt value. This sets the pounds member of incognito to 276.8. Because it uses the constructor, this assignment also sets the stone and pds_left members of the class. Similarly, the second assignment converts a type int value to type double and then uses Stonewt(double) to set all three member values in the process.

Finally, note the following function call:

display(422, 2);    // convert 422 to double, then to Stonewt

The prototype for display() indicates that its first argument should be the Stonewt object. (Either a Stonewt or a Stonewt & formal parameter matches a Stonewt argument.) Confronted with an int argument, the compiler looks for a Stonewt(int) constructor to convert the int to the desired Stonewt type. Failing to find that constructor, the compiler looks for a constructor with some other built-in type to which an int can be converted. The Stonewt(double) constructor fits the bill. So the compiler converts int to double and then uses Stonewt(double) to convert the result to a Stonewt object.