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 to create two _user-defined_ manipulators called `tab` and `roman`. The `tab` manipulator should output a **`\t`** to the _output_ stream and the `roman` manipulator should receive a **roman string** as an argument and send its **decimal** equivalent to the _output_ stream.

# Coding solution	
Here is a solution to the problem above.	                        

// User-defined manipulators

#include <iostream>

std :: ostream& tab ( std :: ostream& o ) 
{
	return o << "\t" ;
}

class roman
{
	private :
		
		std :: string str ;

	public :
		
		roman ( std :: string s ) 
		{
			str = s ;
		}

		friend std :: ostream& operator << ( std :: ostream&, const roman& ) ;
} ;

std :: ostream& operator << ( std :: ostream& o, const roman& r ) 
{

	struct key
	{
		char ch ;
		int val ;
	} ;

	key z[ ] = {
					{'m', 1000}, 
					{'d', 500}, 
					{'c', 100}, 
					{'l', 50}, 
					{'x', 10}, 
					{'v', 5}, 
					{'i', 1}
			   } ; 

	int num = 0 ;
	int prev ;
	int sz = sizeof ( z ) / sizeof ( z[ 0 ] ) ;
	
	for ( int i = 0 ; i < r.str.length ( ) ; i++ ) 
	{
		int j ;
		
		for ( j = 0 ; j < sz ; j++ ) 
		{
			if ( z[ j ].ch == r.str[ i ] ) 
			{
				break ;
			}
		}
		
		num = num + z[ j ].val ;
		if ( i != 0 && prev < z[ j ].val ) 
			num = num - 2 * prev ;

		prev = z[ j ].val ;
	}
	
	o << num ;
	
	return o ;			
}

int main( ) 
{
	std :: string str1 = "viii" ;
	std :: string str2 = "mcmxcviii" ;

	std :: cout << "Roman: " << str1 << tab << "Dec: " << roman ( str1 ) << std :: endl;
	std :: cout << "Roman: " << str2 << tab << "Dec: " << roman ( str2 ) << std :: endl;

	return 0 ;
}


# Explanation	 	                        

To understand how to develop a **zero-argument** manipulator we need to understand the internal working of some existing manipulator, say `endl`. `endl` is simply a function that takes as its argument an `ostream` reference. The declaration for `endl( )` in `iostream` looks like this.

```C++
std :: ostream& endl ( std :: ostream& ) ;
```

Consider the statement:

```C++
std :: cout << std :: endl ;
```

Since `<<` is an overloaded operator, internally this statement becomes,

```C++
std :: cout.operator << ( std :: endl ) ;
```

`endl( )` being a function that is being passed to the overloaded operator is a _pointer_ to a function. The `<<` operator has been defined in `iostream` as follows:

```C++
std :: ostream& ostream :: operator << (ostream& ( *_f)(ostream&)){
	return ( *_f )( *this ) ;
}
```

This indicates that when we pass the address of `endl( )` to this function it collects it in a _pointer_ to a function that receives an `ostream` reference and returns an `ostream` reference. If you observe carefully this matches the prototype of the `endl( )` function. Since this operator function is called through the `cout` object the `this` pointer contains the address of `cout`. Hence `*this` yields the object. This object is then passed to the `endl( )` function through the statement.
```C++
( *_f )( *this ) ;
```
When called, all the `endl( )` function does is emit a `‘\n’` to the output stream.

Our _user-defined_ `tab( )` manipulator function works exactly same as `endl( )`, except that it emits a `‘\t’` instead of a `‘\n’`.

To implement this `roman( )` manipulator we need to define a _class_ called `roman`. This class consists of a **constructor** and an overloaded `<<` operator function. 
Observe the following statement carefully:
```C++
std :: cout << roman ( str1 ) ;
```

Here `roman ( str1 )` creates a temporary object of the type `roman`. Naturally, while creating this temporary object, the **constructor** gets called and the value passed to it gets set in the **private** variable `str`. This temporary object and the `cout` object are then passed to the overloaded operator `<< ( )` function. Note that in the case of a **friend**, the call to the **operator** function doesn’t get converted into the form:
```C++
std :: cout.operator << ( roman ( str1 ) ) ;
```
Within the **operator** function, we have converted the value in `str` into its **decimal** equivalent and outputted it using the reference of the `cout` object. At the end, we return the **reference**. This returning of the _reference_ is necessary if we are to use the manipulator in a cascaded `cout`.

Learn how to create manipulators to output a tab and display a roman number as a decimal.

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

User-defined Manipulators

Problem