5 - Pointers & References

Question 1

Diff btn references and pointers

Answer 1

• there are no null references
• all references require initialization when being created
• cannot be used to refer to a different object

Question 2

Initializing a reference: a reference to a const can be initialized with a literal or temp value

Answer 2

const double &cd = 12.3; // No Error
double &cd = 12.3; // Error!

When a reference to const is initialized with a literal, the ref is set to refer to a temp location that is initialized with the literal. cd doesn’t ref to the literal 12.3 but to a temporary of type double that has been init to 12.3.

const double &cd = 12.3; // No Error
template 
T add(const T &a, const T &b) {
return a + b;
}
//…
const string &greeting =
add(string(“Hello”), string(“, World”)); // No Error!

Ref greeting refers to the unnamed temp string return value in the func add. When the temporary is used to initialize a reference to const, the temp will exist as long as the reference that it refers too. It is not deleted when the function add exits

Question 3

Calling with mismatched types

Answer 3

void swapint(int & aInt, int & bInt){
int temp;
temp = aInt;
aInt = bInt;
bInt = temp;
}
int main() {
long a = 3, b = 5;
swapint(a,b);
}

Casted to two temporary ints to be passed in the constructor, so when you print after the swap, the values of a and b will still be the same. Solution: Labeling the method as explicit

Question 4

const pointer and const data

Answer 4

left of * -> const data

right of * -> const pointer

Question 5

Passing an array

Answer 5

void myFunction (int array[]) {…}
void myFunction (int *array) {…}

Question 6

Strings

Answer 6

c++ represents strings as arrays of characters that include ‘\0’ at the end. The value of the string is the address of the first character

Question 7

Returning an object vs returning a reference

Answer 7

Returning an object invokes the copy cons., while returning a reference does not.