Chapter 14. Overloaded Operations and Conversions

Exercise 14.1:

In what ways does an overloaded operator differ from a built-in operator? In what ways are overloaded operators the same as the built-in operators?

Differ

1. We can call an overloaded operator function directly.
2. An overloaded operator function must either be a member of a class or have at least one parameter of class type.
3. A few operators guarantee the order in which operands are evaluated. These overloaded versions of these operators do not preserve order of evaluation and/or short-circuit evaluation, it is usually a bad idea to overload them.

In particular, the operand-evaluation guarantees of the logical AND, logical OR, and comma operators are not preserved, Moreover, overloaded versions of && or || operators do not preserve short-circuit evaluation properties of the built-in operators. Both operands are always evaluated.

Same

• An overloaded operator has the same precedence and associativity as the corresponding built-in operator.

Exercise 14.2:

Write declarations for the overloaded input, output, addition, and compound-assignment operators for Sales_data.

hpp | cpp

Exercise 14.3:

Both string and vector define an overloaded == that can be used to compare objects of those types. Assuming svec1 and svec2 are vectors that hold strings, identify which version of == is applied in each of the following expressions:

• (a) "cobble" == "stone"
• (b) svec1[0] == svec2[0]
• (c) svec1 == svec2
• (d) "svec1[0] == "stone"

(a) neither. (b) string (c) vector (d) string

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Reference

• Why does the following not invoke the overloaded operator== (const String &, const String &)? “cobble” == “stone”

Exercise 14.4:

Explain how to decide whether the following should be class members:

• (a) %
• (b) %=
• (c) ++
• (d) ->
• (e) <<
• (f) &&
• (g) ==
• (h) ()

(a) symmetric operator. Hence, non-member

(b) changing state of objects. Hence, member

(c) changing state of objects. Hence, member

(d) = [] () -> must be member

(e) non-member

(f) symetric , non-member

(g) symetric , non-member

(h) = [] () -> must be member

Exercise 14.5:

In exercise 7.40 from 7.5.1 (p. 291) you wrote a sketch of one of the following classes. Decide what, if any, overloaded operators your class should provide.

Such as Book

hpp | cpp | test

Exercise 14.6:

Define an output operator for your Sales_data class.

see [Exercise 14.2](#Exercise 14.2).

Exercise 14.7:

Define an output operator for you String class you wrote for the exercises in 13.5 (p. 531).

hpp | cpp | Test

Exercise 14.8:

Define an output operator for the class you chose in exercise 7.40 from 7.5.1 (p. 291).

see [Exercise 14.5](#Exercise 14.5)

Exercise 14.9:

Define an input operator for your Sales_data class.

see [Exercise 14.2](#Exercise 14.2).

Exercise 14.10:

Describe the behaviour of the Sales_data input operator if given the following input:

• (a) 0-201-99999-9 10 24.95

• (b) 10 24.95 0-210-99999-9

• (a) correct format.

• (b) ilegal input. But 0-210-99999-9 will be converted to a float stored in this object. As a result, the data inside will be a wrong one. Output: 10 24 22.8 0.95

check Test

Exercise 14.11:

What, if anything, is wrong with the following Sales_data input operator? What would happen if we gave this operator the data in the previous exercise?

istream& operator>>(istream& in, Sales_data& s)
{
    double price;
    in >> s.bookNo >> s.units_sold >> price;
    s.revenue = s.units_sold * price;
    return in;
}

no input check. nothing happend.

Exercise 14.12:

Define an input operator for the class you used in exercise 7.40 from 7.5.1 (p. 291). Be sure the operator handles input errors.

see [Exercise 14.5](#Exercise 14.5)

Exercise 14.13:

Which other arithmetic operators (Table 4.1 (p. 139)), if any, do you think Sales_data ought to support? Define any you think the class should include.

no others.

Exercise 14.14:

Why do you think it is more efficient to define operator+ to call operator+= rather than the other way around?

Discussing on SO.

Exercise 14.15:

Should the class you chose for exercise 7.40 from 7.5.1 (p. 291) define any of the arithmetic operators? If so, implement them. If not, explain why not.

hpp | cpp | Test

Exercise 14.16:

Define equality and inequality operators for your StrBlob (12.1.1, p. 456), StrBlobPtr (12.1.6, p. 474), StrVec (13.5, p.526), and String (13.5, p. 531) classes.