Using A Smart Pointer Can We Iterate Through A Container?
Yes. A container is a collection of elements or objects. It helps to properly organize and store the data. Stacks, linked lists, arrays are examples of containers. Following program shows how to iterate through a container using a smart pointer.
#include
class smartpointer
{
private
int *p ; // ordinary pointer
public
smartpointer ( int n )
{
p = new int [ n ] ;
int *t = p ;
for ( int i = 0 ; i <= 9 ; i++ )
*t++ = i * i ;
}
int* operator ++ ( int )
{
return p++ ;
}
int operator * ( )
{
return *p ;
}
} ;
void main( )
{
smartpointer sp ( 10 ) ;
for ( int i = 0 ; i <= 9 ; i++ )
cout << *sp++ << endl ;
}
Here, sp is a smart pointer. When we say *sp, the operator * ( ) function gets called. It returns the integer being pointed to by p. When we say sp++ the operator ++ ( ) function gets called. It increments p to point to the next element in the array and then returns the address of this new location.
Is It Possible For The Objects To Read And Write Themselves?
Yes! This can be explained with the help of following example
#include
#include
class employee
{
private
char name [ 20 ] ;
int age ;
float salary ;
public
void getdata( )
{
cout << "Enter name, age and salary of employee : " ;
cin >> name >> age >> salary ;
}
void store( )
{
ofstream file ;
file.open ( "EMPLOYEE.DAT", ios::app | ios::binary ) ;
file.write ( ( char * ) this, sizeof ( *this ) ) ;
file.close( ) ;
}
void retrieve ( int n )
{
ifstream file ;
file.open ( "EMPLOYEE.DAT", ios::binary ) ;
file.seekg ( n * sizeof ( employee ) ) ;
file.read ( ( char * ) this, sizeof ( *this ) ) ;
file.close( ) ;
}
void show( )
{
cout << "Name : " << name
<< endl << "Age : " << age
<< endl << "Salary :" << salary << endl ;
}
} ;
void main( )
{
employee e [ 5 ] ;
for ( int i = 0 ; i <= 4 ; i++ )
{
e [ i ].getdata( ) ;
e [ i ].store( ) ;
}
for ( i = 0 ; i <= 4 ; i++ )
{
e [ i ].retrieve ( i ) ;
e [ i ].show( ) ;
}
}
Here, employee is the class whose objects can write and read themselves. The getdata( ) function has been used to get the data of employee and store it in the data members name, age and salary. The store( ) function is used to write an object to the file. In this function a file has been opened in append mode and each time data of current object has been stored after the last record (if any) in the file.Function retrieve( ) is used to get the data of a particular employee from the file. This retrieved data has been stored in the data members name, age and salary. Here this has been used to store data since it contains the address of the current object. The function show( ) has been used to display the data of employee.
Why Is It Necessary To Use A Reference In The Argument To The Copy Constructor?
If we pass the copy constructor the argument by value, its copy would get constructed using the copy constructor. This means the copy constructor would call itself to make this copy. This process would go on and on until the compiler runs out of memory. This can be explained with the help of following example
class sample
{
int i ;
public
sample ( sample p )
{
i = p.i ;
}
} ;
void main( )
{
sample s ;
sample s1 ( s ) ;
}
While executing the statement sample s1 ( s ), the copy constructor would get called. As the copy construct here accepts a value, the value of s would be passed which would get collected in p. We can think of this statement as sample p = s. Here p is getting created and initialized. Means again the copy constructor would get called. This would result into recursive calls. Hence we must use a reference as an argument in a copy constructor.
What Is C++?
Released in 1985, C++ is an object-oriented programming language created by Bjarne Stroustrup. C++ maintains almost all aspects of the C language, while simplifying memory management and adding several features - including a new datatype known as a class (you will learn more about these later) - to allow object-oriented programming. C++ maintains the features of C which allowed for low-level memory access but also gives the programmer new tools to simplify memory management.
C++ used for
C++ is a powerful general-purpose programming language. It can be used to create small programs or large applications. It can be used to make CGI scripts or console-only DOS programs. C++ allows you to create programs to do almost anything you need to do. The creator of C++, Bjarne Stroustrup, has put together a partial list of applications written in C++.
What Is A Modifier In C++?
A modifier, also called a modifying function is a member function that changes the value of at least one data member. In other words, an operation that modifies the state of an object. Modifiers are also known as 'mutators'. Example: The function mod is a modifier in the following code snippet
class test
{
int x,y;
public
test()
{
x=0; y=0;
}
void mod()
{ x=10;
y=15;
}
};
What Is An Accessor In C++?
An accessor is a class operation that does not modify the state of an object in C++. The accessor functions need to be declared as const operations.
Differentiate Between A Template Class And Class Template In C++?
Template class: A generic definition or a parameterized class not instantiated until the client provides the needed information. It's jargon for plain templates.
Class template: A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It's jargon for plain classes.
When Does A Name Clash Occur In C++?
A name clash occurs when a name is defined in more than one place. For example., two different class libraries could give two different classes the same name. If you try to use many class libraries at the same time, there is a fair chance that you will be unable to compile or link the program because of name clashes.
Define Namespace In C++?
It is a feature in C++ to minimize name collisions in the global name space. This namespace keyword assigns a distinct name to a library that allows other libraries to use the same identifier names without creating any name collisions. Furthermore, the compiler uses the namespace signature for differentiating the definitions.
What Is The Use Of 'using' Declaration In C++?
A using declaration in C++ makes it possible to use a name from a namespace without the scope operator.
What Is An Iterator Class In C++?
A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An iterator is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order. The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or according to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to and update of the elements of a container class. The simplest and safest iterators are those that permit read-only access to the contents of a container class.
What Is An Incomplete Type In C++?
Incomplete types refers to pointers in which there is non availability of the implementation of the referenced location or it points to some location whose value is not available for modification.
int *i=0x400 //i points to address 400
*i=0; //set the value of memory location pointed by i.
Incomplete types are otherwise called uninitialized pointers.
What Is A Dangling Pointer In C++?
A dangling pointer arises when you use the address of an object after its lifetime is over. This may occur in situations like returning addresses of the automatic variables from a function or using the address of the memory block after it is freed. The following code snippet shows this
class Sample
{
public:int *ptr; Sample(int i)
{
ptr = new int(i);
}
~Sample()
{
delete ptr;
}
void PrintValO
{
cout« "The value is " « *ptr;
}
};
void SomeFunc(Sample x)
{
cout« "Say i am in someFunc " « endl;
}
int main()
{
Sample si = 10;
SomeFunc(sl);
sl.PrintVal();
}
In the above example when PrintVal() function is called it is called by the pointer that has been freed by the destructor in SomeFunc.
Differentiate Between The Message And Method In C++?
Message in C++
Objects communicate by sending messages to each other.
A message is sent to invoke a method in C++.
Method in C++
Provides response to a message.
It is an implementation of an operation in C++.
What Is An Adaptor Class Or Wrapper Class In C++?
A class that has no functionality of its own is an Adaptor class in C++. Its member functions hide the use of a third party software component or an object with the non-compatible interface or a non-object-oriented implementation.
What Is A Null Object In C++?
It is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member function that is supposed to return an object with some specified properties but cannot find such an object.
What Is Class Invariant In C++?
A class invariant is a condition that defines all valid states for an object. It is a logical condition to ensure the correct working of a class. Class invariants must hold when an object is created, and they must be preserved under all operations of the class. In particular all class invariants are both preconditions and post-conditions for all operations or member functions of the class.
What Do You Mean By Stack Unwinding In C++?
Stack unwinding in C++ is a process during exception handling when the destructor is called for all local objects between the place where the exception was thrown and where it is caught.
Define Pre-condition And Post-condition To A Member Function In C++?
Precondition: A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold. For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation.
Post-condition: A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false. For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation.
Yes. A container is a collection of elements or objects. It helps to properly organize and store the data. Stacks, linked lists, arrays are examples of containers. Following program shows how to iterate through a container using a smart pointer.
#include
class smartpointer
{
private
int *p ; // ordinary pointer
public
smartpointer ( int n )
{
p = new int [ n ] ;
int *t = p ;
for ( int i = 0 ; i <= 9 ; i++ )
*t++ = i * i ;
}
int* operator ++ ( int )
{
return p++ ;
}
int operator * ( )
{
return *p ;
}
} ;
void main( )
{
smartpointer sp ( 10 ) ;
for ( int i = 0 ; i <= 9 ; i++ )
cout << *sp++ << endl ;
}
Here, sp is a smart pointer. When we say *sp, the operator * ( ) function gets called. It returns the integer being pointed to by p. When we say sp++ the operator ++ ( ) function gets called. It increments p to point to the next element in the array and then returns the address of this new location.
Is It Possible For The Objects To Read And Write Themselves?
Yes! This can be explained with the help of following example
#include
#include
class employee
{
private
char name [ 20 ] ;
int age ;
float salary ;
public
void getdata( )
{
cout << "Enter name, age and salary of employee : " ;
cin >> name >> age >> salary ;
}
void store( )
{
ofstream file ;
file.open ( "EMPLOYEE.DAT", ios::app | ios::binary ) ;
file.write ( ( char * ) this, sizeof ( *this ) ) ;
file.close( ) ;
}
void retrieve ( int n )
{
ifstream file ;
file.open ( "EMPLOYEE.DAT", ios::binary ) ;
file.seekg ( n * sizeof ( employee ) ) ;
file.read ( ( char * ) this, sizeof ( *this ) ) ;
file.close( ) ;
}
void show( )
{
cout << "Name : " << name
<< endl << "Age : " << age
<< endl << "Salary :" << salary << endl ;
}
} ;
void main( )
{
employee e [ 5 ] ;
for ( int i = 0 ; i <= 4 ; i++ )
{
e [ i ].getdata( ) ;
e [ i ].store( ) ;
}
for ( i = 0 ; i <= 4 ; i++ )
{
e [ i ].retrieve ( i ) ;
e [ i ].show( ) ;
}
}
Here, employee is the class whose objects can write and read themselves. The getdata( ) function has been used to get the data of employee and store it in the data members name, age and salary. The store( ) function is used to write an object to the file. In this function a file has been opened in append mode and each time data of current object has been stored after the last record (if any) in the file.Function retrieve( ) is used to get the data of a particular employee from the file. This retrieved data has been stored in the data members name, age and salary. Here this has been used to store data since it contains the address of the current object. The function show( ) has been used to display the data of employee.
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| Spotify Technology Frequently Asked C++ Interview Questions Answers |
Why Is It Necessary To Use A Reference In The Argument To The Copy Constructor?
If we pass the copy constructor the argument by value, its copy would get constructed using the copy constructor. This means the copy constructor would call itself to make this copy. This process would go on and on until the compiler runs out of memory. This can be explained with the help of following example
class sample
{
int i ;
public
sample ( sample p )
{
i = p.i ;
}
} ;
void main( )
{
sample s ;
sample s1 ( s ) ;
}
While executing the statement sample s1 ( s ), the copy constructor would get called. As the copy construct here accepts a value, the value of s would be passed which would get collected in p. We can think of this statement as sample p = s. Here p is getting created and initialized. Means again the copy constructor would get called. This would result into recursive calls. Hence we must use a reference as an argument in a copy constructor.
What Is C++?
Released in 1985, C++ is an object-oriented programming language created by Bjarne Stroustrup. C++ maintains almost all aspects of the C language, while simplifying memory management and adding several features - including a new datatype known as a class (you will learn more about these later) - to allow object-oriented programming. C++ maintains the features of C which allowed for low-level memory access but also gives the programmer new tools to simplify memory management.
C++ used for
C++ is a powerful general-purpose programming language. It can be used to create small programs or large applications. It can be used to make CGI scripts or console-only DOS programs. C++ allows you to create programs to do almost anything you need to do. The creator of C++, Bjarne Stroustrup, has put together a partial list of applications written in C++.
What Is A Modifier In C++?
A modifier, also called a modifying function is a member function that changes the value of at least one data member. In other words, an operation that modifies the state of an object. Modifiers are also known as 'mutators'. Example: The function mod is a modifier in the following code snippet
class test
{
int x,y;
public
test()
{
x=0; y=0;
}
void mod()
{ x=10;
y=15;
}
};
What Is An Accessor In C++?
An accessor is a class operation that does not modify the state of an object in C++. The accessor functions need to be declared as const operations.
Differentiate Between A Template Class And Class Template In C++?
Template class: A generic definition or a parameterized class not instantiated until the client provides the needed information. It's jargon for plain templates.
Class template: A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It's jargon for plain classes.
When Does A Name Clash Occur In C++?
A name clash occurs when a name is defined in more than one place. For example., two different class libraries could give two different classes the same name. If you try to use many class libraries at the same time, there is a fair chance that you will be unable to compile or link the program because of name clashes.
Define Namespace In C++?
It is a feature in C++ to minimize name collisions in the global name space. This namespace keyword assigns a distinct name to a library that allows other libraries to use the same identifier names without creating any name collisions. Furthermore, the compiler uses the namespace signature for differentiating the definitions.
What Is The Use Of 'using' Declaration In C++?
A using declaration in C++ makes it possible to use a name from a namespace without the scope operator.
What Is An Iterator Class In C++?
A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An iterator is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order. The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or according to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to and update of the elements of a container class. The simplest and safest iterators are those that permit read-only access to the contents of a container class.
What Is An Incomplete Type In C++?
Incomplete types refers to pointers in which there is non availability of the implementation of the referenced location or it points to some location whose value is not available for modification.
int *i=0x400 //i points to address 400
*i=0; //set the value of memory location pointed by i.
Incomplete types are otherwise called uninitialized pointers.
What Is A Dangling Pointer In C++?
A dangling pointer arises when you use the address of an object after its lifetime is over. This may occur in situations like returning addresses of the automatic variables from a function or using the address of the memory block after it is freed. The following code snippet shows this
class Sample
{
public:int *ptr; Sample(int i)
{
ptr = new int(i);
}
~Sample()
{
delete ptr;
}
void PrintValO
{
cout« "The value is " « *ptr;
}
};
void SomeFunc(Sample x)
{
cout« "Say i am in someFunc " « endl;
}
int main()
{
Sample si = 10;
SomeFunc(sl);
sl.PrintVal();
}
In the above example when PrintVal() function is called it is called by the pointer that has been freed by the destructor in SomeFunc.
Differentiate Between The Message And Method In C++?
Message in C++
Objects communicate by sending messages to each other.
A message is sent to invoke a method in C++.
Method in C++
Provides response to a message.
It is an implementation of an operation in C++.
What Is An Adaptor Class Or Wrapper Class In C++?
A class that has no functionality of its own is an Adaptor class in C++. Its member functions hide the use of a third party software component or an object with the non-compatible interface or a non-object-oriented implementation.
What Is A Null Object In C++?
It is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member function that is supposed to return an object with some specified properties but cannot find such an object.
What Is Class Invariant In C++?
A class invariant is a condition that defines all valid states for an object. It is a logical condition to ensure the correct working of a class. Class invariants must hold when an object is created, and they must be preserved under all operations of the class. In particular all class invariants are both preconditions and post-conditions for all operations or member functions of the class.
What Do You Mean By Stack Unwinding In C++?
Stack unwinding in C++ is a process during exception handling when the destructor is called for all local objects between the place where the exception was thrown and where it is caught.
Define Pre-condition And Post-condition To A Member Function In C++?
Precondition: A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold. For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation.
Post-condition: A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false. For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation.
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