Learn C++ References & Pointers
const Reference
In C++, pass-by-reference with
const can be used for a function where the parameter(s) won’t change inside the function.
This saves the computational cost of making a copy of the argument.
int triple(int const &i) {
return i * 3;
}
Pointers
In C++, a pointer variable stores the memory address of something else. It is created using the
* sign.
int* pointer = &gum;
References
In C++, a reference variable is an alias for another object. It is created using the
& sign. Two things to note:- Anything done to the reference also happens to the original.
- Aliases cannot be changed to alias something else.
int &sonny = songqiao;
Memory Address
In C++, the memory address is the location in the memory of an object. It can be accessed with the “address of” operator,
&.
Given a variable
porcupine_count, the memory address can be retrieved by printing out &porcupine_count. It will return something like: 0x7ffd7caa5b54.
std::cout << &porcupine_count << "\n";
Dereference
In C++, a dereference reference operator,
*, can be used to obtain the value pointed to by a pointer variable.
int gum = 3;
// * on left side is a pointer
int* pointer = &gum;
// * on right side is a dereference of that pointer
int dereference = *pointer;
Pass-By-Reference
In C++, pass-by-reference refers to passing parameters to a function by using references.
It allows the ability to:
- Modify the value of the function arguments.
- Avoid making copies of a variable/object for performance reasons.
void swap_num(int &i, int &j) {
int temp = i;
i = j;
j = temp;
}
int main() {
int a = 100;
int b = 200;
swap_num(a, b);
std::cout << "A is " << a << "\n";
std::cout << "B is " << b << "\n";
}
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