# Replace switch statement by function pointers

//————————————————————————————
// 1.2 Introductory Example or How to Replace a Switch-Statement
// Task: Perform one of the four basic arithmetic operations specified by the
// characters ‘+’, ‘-‘, ‘*’ or ‘/’.

// The four arithmetic operations ... one of these functions is selected
// at runtime with a switch or a function pointer
float Plus (float a, float b) { return a+b; }
float Minus (float a, float b) { return a-b; }
float Multiply(float a, float b) { return a*b; }
float Divide (float a, float b) { return a/b; }
// Solution with a switch-statement - specifies which operation to execute
void Switch(float a, float b, char opCode)
{
float result;
// execute operation
switch(opCode)
{
case '+' : result = Plus (a, b); break;
case '-' : result = Minus (a, b); break;
case '*' : result = Multiply (a, b); break;
case '/' : result = Divide (a, b); break;
}
cout << "Switch: 2+5=" << result << endl; // display result
}
// Solution with a function pointer - is a function pointer and points to
// a function which takes two floats and returns a float. The function pointer
// "specifies" which operation shall be executed.
void Switch_With_Function_Pointer(float a, float b, float (*pt2Func)(float, float))
{
float result = pt2Func(a, b); // call using function pointer
cout << "Switch replaced by function pointer: 2-5="; // display result
cout << result << endl;
}
// Execute example code
void Replace_A_Switch()
{
cout << endl << "Executing function 'Replace_A_Switch'" << endl;
Switch(2, 5, /* '+' specifies function 'Plus' to be executed */ '+');
Switch_With_Function_Pointer(2, 5, /* pointer to function 'Minus' */ &Minus);
}