Why does C++ allow default arguments in functions, and how are they resolved at runtime?

C++ allows default arguments in functions to enhance flexibility, improve code readability, and reduce repetitive function overloading. Default arguments are values provided in a function declaration that are automatically used when no argument is passed for those parameters during a function call.

Why does C++ allow defaults arguments?

Simplifies Function Calls

By providing defaults values, a single function can handle multiple scenarios without requiring explicit arguments for each call. For example:

void greet(std::string name = "Guest") {
    std::cout << "Hello, " << name << "!\n";
}
greet();              // Outputs: Hello, Guest!
greet("Alice");       // Outputs: Hello, Alice!

Reduces Overloading

Instead of writing multiple overloaded functions, you can define a single function with default arguments, reducing redundancy and maintenance effort.

Improves Readability

Code becomes clearer as the intent of optional parameters is directly visible in the function signature.

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How are defaults arguments resolved?

Default arguments are resolved at compile time, not runtime. When a function is called without specifying some arguments, the compiler substitutes the missing arguments with their default values. For example:

void display(int x = 10, int y = 20) {
    std::cout << x << ", " << y << "\n";
}
display();       // Compiler rewrites as display(10, 20)
display(5);      // Compiler rewrites as display(5, 20)

default arguments

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