Functions are no doubt one of the most important parts of any
programming language. They help us to reuse a particular logic multiple number
of times inside a program and are very easy to modify.
To know basics of functions read the article on Functions in C++.
Here we will be discussing the various forms of functions that
are used in C++. Their use depends upon the task we need to perform.
We know functions contain a return type, function’s name and
argument list. Out of these, the return type and argument list are optional
which give rise to the different forms of functions.
Function forms in C++
Form 1. Function with no return type and no argument
When we do not need to feed any value into a function nor do
we want the function to return some value, we use this form. When a function doesn’t
return any value, we put its return type as void.
General syntax :
void function_name
()
{
// body of function;
//
no return statement;
}
Form 2. Function with return value but no argument
When we do not need to pass values to a function but we wish
to return some value, we use this form. The return type should match the type
of value being returned. If they do not match, the returned value is converted
into the return type value which might cause loss in information.
General syntax :
return_type
function_name ()
{
// body of the function;
// return statement;
}
where return_type
can be any C++ datatype (primitive, derived or user-defined) except void.
Form 3. Function with no
return type but with argument list
This form of a function can be used when we want to pass
certain values into the function for evaluation but we do not want the function
to return a value. As the function returns no value, we use void as the return
type.
General Syntax :
void function_name (argument
list)
{
// body of function;
// no return statement;
}
Form 4. Function with return type and argument list
This form is used if we want to pass the values to the
function, perform the required operations and then return back the result
value.
General Syntax :
return_type
function_name (argument list)
{
//body of the function;
//return statement;
}
For comparison, we will write the same program to find greater
of the 2 integers entered by the user, separately using all four forms of a
function named max.
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