What is manipulator in C++?

1. Standard Manipulators

These are built-in manipulators that do not require arguments.

• endl: Inserts a newline character and flushes the output buffer.

  std::cout << "Hello" << std::endl;  // Outputs "Hello" followed by a newline

• setw: Sets the width of the next input/output operation.

  std::cout << std::setw(10) << "Hi";  // Outputs "Hi" padded to 10 characters

• setprecision: Sets the number of digits after the decimal point for floating-point numbers.

  std::cout << std::setprecision(3) << 3.14159;  // Outputs "3.14"

• fixed and scientific: Used to display floating-point numbers in fixed-point or scientific notation.

  std::cout << std::fixed << 123.456;     // Outputs "123.456"
  std::cout << std::scientific << 123.456;  // Outputs "1.234560e+02"

2. Custom Manipulators

You can also create custom manipulators to define specific behaviors or formats for input/output operations.

Example:

std::ostream& customEndl(std::ostream& out) {
    out << "\n--- End of Line ---\n";
    return out;
}

std::cout << "Hello" << customEndl;  // Outputs "Hello" followed by a custom message

Commonly Used Manipulators:

• hex, oct, and dec: Used to change the number base (hexadecimal, octal, or decimal) for integer output.

  std::cout << std::hex << 255;  // Outputs "ff"

• showpos: Displays the positive sign for numbers.

  std::cout << std::showpos << 42;  // Outputs "+42"

• left, right, internal: Aligns output to the left, right, or internally within the specified width.

Sources:

• GeeksforGeeks: Manipulators in C++
• cplusplus.com: I/O Manipulators