CPP Function Default Parameters

Function and Default Parameters.

• A default value is a value to use if none is supplied.
• You can setup default values to parameters within the prototyping of the function. You should not do this at the implementation of the function.
  Default Parameters example:

  Source code

  Result

  // Demonstrates use // of default parameter values #include <iostream> // Prototyping of the function int getVolume(int length, int width = 25, int height = 1); int main() { int length = 100; int width = 50; int height = 2; int volume; // The result of this should be 100*50*2=10000 volume = getVolume(length, width, height); std::cout << "1.volume equals: " << volume << "\n"; // The result of this should be 100*50*1=5000 volume = getVolume(length, width); std::cout << "2.volume equals: " << volume << "\n"; // The result of this should be 100*25*1=2500 volume = getVolume(length); std::cout << "3.volume equals: " << volume << "\n"; return 0; } // Implementation of the function int getVolume(int length, int width, int height) { return (length * width * height); }

  1.volume equals: 10000 2.volume equals: 5000 3.volume equals: 2500

  Rules in assigning default parameters:
  • You can assign a default value to Param2 only if you have assigned a default value to Param3.
  • You can assign a default value to Param1 only if you've assigned default values to both Param2 and Param3.

  You can download this example here (needed tools can be found in the right menu on this page).