Authors:
Walter Savitch ,julia Lobur
Chapter:
Defining Classes
Exercise:
Self-test Exercises
Question:5 | ISBN:9780321531346 | Edition: 7
Question
Here is an initialization of a structure type. Tell what happens with each
initialization. Note any problems with these initializations.
struct Date
{
int month;
int day;
int year;
};
a. Date due_date = {12, 21};
b. Date due_date = {12, 21, 2022};
c. Date due_date = {12, 21, 20, 22};
d. Date due_date = {12, 21, 22};
Answer
Conisder the given data:
struct Date
{
int month;
int day;
int year;
};
a)
Date due_date = {12, 21};
Valid, but the year member is uninitialized.
Explanation:
- In this initialization, the
monthmember ofdue_datewill be set to 12, thedaymember will be set to 21, and theyearmember will have an unspecified value. - This is because only the first two members (month and day) are explicitly provided in the initializer.
- The
yearmember will take whatever value happens to be in memory at the location reserved for theyearmember of the structure. - This can lead to unexpected behavior, as the
yearvalue will be uninitialized.
b)
Date due_date = {12, 21, 2022};
Valid, all members are explicitly initialized.
Explanation:
- In this initialization, all three members of
due_dateare provided with values. - The
monthmember will be set to 12, thedaymember will be set to 21, and theyearmember will be set to 2022. - This initialization is valid and sets all members of the structure to specific values.
c)
Date due_date = {12, 21, 20, 22};
Invalid, too many initializer values.
Explanation:
- In this initialization, four values are provided in the initializer, but the
Datestructure only has three members. - The first three values (12, 21, and 20) will be assigned to the
month,day, andyearmembers of thedue_datestructure, respectively. - The fourth value (22) will have no place to go, and this initialization will likely result in a compilation error because there are too many initializer values.
d)
Date due_date = {12, 21, 22};
Valid, all members are explicitly initialized.
Explanation:
- In this initialization, all three members of
due_dateare provided with values. - The
monthmember will be set to 12, thedaymember will be set to 21, and theyearmember will be set to 22. - This initialization is valid and sets all members of the structure to specific values.