Gain insights into dynamic memory allocation, creating classes, and functions. Delve into inheritance, I/O, exception handling. Explore 90+ examples to master advanced C++ functionalities.

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If you’re looking to sharpen up your C++ programming skills, then you’re in the right place. You will start with learning about dynamic memory allocation, how to create classes, and constructors. 

In the latter half of the course, inheritance, functions, I/O, exception handling, and more. Throughout the course, you will study over 90 carefully designed examples aimed to enhance your understanding of the C++ language.  

By the time you finish this course, you will be able to use more advanced functionality in your C++ programs.

C++ Programming for Experienced Engineers

# Problem

Write a program that has a function `findmax( )` that receives a variable number of arguments and finds and returns the maximum out of them.

# Coding solution

Here is a solution to the above problem.



#include <iostream>
#include <cstdarg>


int findmax ( int, ...) ;

int main( )
{
	int  max ;

	max = findmax ( 5, 23, 15, 1, 92, 50 ) ;
	std :: cout << "maximum = " << max << std :: endl ;
	
	max = findmax ( 3, 100, 300, 29 ) ;
	std :: cout << "maximum = " << max << std :: endl ;
	return 0 ;
}

int findmax ( int count, ... )
{
	int  max, i, num ;

	va_list  ptr ;

	va_start ( ptr, count ) ;
	max = va_arg ( ptr, int ) ;

	for ( i = 1 ; i < count ; i++ )
	{
		num = va_arg ( ptr, int ) ;
		if ( num > max )
			max = num ;
	}

	return ( max ) ;
}


# Explanation	 	                        

Look at the prototype of `findmax( )`. The ellipses `( … )` indicate that *the number of arguments after the first argument would be variable.* 

Observe the two calls to `findmax( )`. In the _first call_, _we passed 6 arguments_. In the _second_, _we passed 4 arguments_.


There are **three** macros available in the file `stdarg.h` called `va_start`, `va_arg` and `va_list`, which allow us to handle this situation. These macros provide a method for accessing the arguments of the function *when a function takes a fixed number of arguments followed by a variable number of arguments.* The fixed number of arguments are accessed in the normal way, whereas the optional arguments are accessed using the macros `va_start` and `va_arg`. 

> Out of these macros, `va_start` is used to initialize a pointer to the beginning of the list of optional arguments. On the other hand, the macro `va_arg` is used to advance the pointer to the next argument.
 
Here we are making two calls to `findmax( )`. The **first time to find maximum out of 5 values**, and **the second time to find maximum out of 3 values**. Note that for each call the *first argument* is the count of arguments that follow the first argument. The value of the first argument passed to the `findmax( )` function is collected in the variable `count`. The `findmax( )` function begins with a declaration of a pointer `ptr` of the type `va_list`. Observe the next statement carefully.

```
va_start ( ptr, tot_num ) ;
```

This statement sets up `ptr` so that it points to the first variable argument in the list. If we are considering the first call to `findmax( )`, `ptr` would now point to **23**. 

```
max = va_arg ( ptr, int )
``` 

The statement would assign the integer being pointed to by `ptr` to **max**. Thus **23** would be assigned to **max**, and `ptr` would now start pointing to the next argument, e.g., **15**. The rest of the program is fairly straightforward. We just keep picking up successive numbers in the list and keep comparing them with the latest value in **max** until all the arguments in the list have been scanned. The final value in **max** is then returned to the `main( )` function.

Learn to find the maximum in a function that receives a variable number of arguments.

Getting Off the Ground

Starters

Basic C++ Examples

Class Organization Examples

Class Constructor Examples

Classes and Objects Examples

More Classes and Objects Examples

Function Examples

Function Overloading Examples

Operator Overloading Examples

Free Store Examples

Inheritance Examples

Virtual Function Examples

Input Output Examples

Template Examples

Exception Handling Examples

STL Examples

Miscellaneous Examples

Conclusion

Variable Number of Arguments

Problem