Cpp functions

Functions

Basics

Functions in C++ must be declared like variables. If they return a value, the type of value must be specified first. If they do not return a value, list the function type as void.

Similar to mel's procedures, you can declare variables in the function declaration as arguments. For instance, if you had a function to multiply two numbers (int num1, int num2)

// function without return value
void myOtherFunction() {
   cout << "Hi there!";
}

// function with return value
int myFunction(int x, int y){
   return x;
}

// function with default values
// (y/z are both optional args now)
//
int myfunction(int x, int y=5, int z=10){
	return x;
}


// c++ does not have named parameters, the common
// approach for calling functions instead is work as follows
window = make_window(
 10,  // xPosition
 20,  // yPosition
 100, // width
 50   // height
);

https://marcoarena.wordpress.com/2014/12/16/bring-named-parameters-in-modern-cpp/

reference args

Reference args allow you to modify arguments within a function without needing to reassign them as a return value. This can actually work out to be 'more efficient' since the values do not need to be copied/recreated inside the function at a different memory addr.

void plus_one( int &a, int &b )
{
	a +=1;
	b +=1;
}


int a = 5;
int b = 10;

plus_one(a, b)
cout << "a=" << a << endl;	  // prints 6
cout << "b=" << b << endl;   // print 11

int main()

Every cpp program has the function definition main. never return a value from this function, this will automatically return 0 on successful run, or 1 on failure. To cpp, the main function is like python's if __name__ == '__main__':.

int main()
{

}

functions as args

In order to use a function as an argument in cpp, you must use a pointer to the argument.

int myfunction( int number, int number2 ){ ... }			// define function

void *(*myfunction)( int, int );									// stores pointer to myfunction with arg int