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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; }


In C++, a pointer variable stores the memory address of something else. It is created using the * sign.

int* pointer = &gum;


In C++, a reference variable is an alias for another object. It is created using the & sign. Two things to note:
  1. Anything done to the reference also happens to the original.
  2. 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";


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;


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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