A First Look at Function

Declaring and Defining a Function

• General form:

return_type name (formal arguments); // declaration
return_type name (formal arguments) body // definition

• Formal arguments (also called parameters), format is

  • type1 name1, type2 name2, ...

• Make return type void if you don't want to return anything

• body is a block (or a try block)

  • Example:

double f(int a, double d) { return a*d; }

Calling a Function

• Recall

double f(int a, double d) { return a*d; }

• To call a function:

name (actual arguments)

• Actual arguments format is

  • argname1, argname2, ...

    • Do not include types!

• Example:

int x = 2;
double y = 5.0;
cout << f(x,y); // prints out 10.0

Note on Terminology

Function Placement

• Functions must be declared in the .cpp file before they are called.

  • So if a function is called in the main function, then it must be declared before main.

  • It can be defined later, as long as it is declared before it is called.

• You cannot define functions inside other functions

  • Well, lambdas are allowed…