Const Correctness in C++

Snippet

Const Correctness in C++

The const keyword declares values that cannot be changed after initialization. Use const for constants like MAX_SIZE that should never mutate. When const appears before a pointer type (const int *ptr), the data pointed to cannot be modified through that pointer. This protects against accidental modifications and helps the compiler optimize code. Const correctness is a best practice that makes code more predictable and maintainable.

snippet.cpp
cpp
#include <iostream>
 
int main() {
    const int MAX_SIZE = 100;
    const double PI = 3.14159;
    
    int value = 10;
    const int *ptr = &value;
    
    std::cout << "Max: " << MAX_SIZE << std::endl;
    std::cout << "Value via ptr: " << *ptr << std::endl;
    
    return 0;
}

Breakdown

const int MAX_SIZE = 100;

Declares a constant integer that cannot be modified

const double PI = 3.14159;

Declares a constant double for mathematical operations

const int *ptr = &value;

Pointer to const int: data cannot be changed via ptr

*ptr

Dereferencing a pointer-to-const to access the value

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Const Correctness in C++

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