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The const keyword transforms a variable into a constant. This means the constant cannot be altered via that constant's identifier. The const keyword can also be applied to a class instance method, such that the method will not alter a class instance's immutable members.
Note that the const keyword is merely a programming aid that provides assurances a constant will not be altered inadvertently. However, it is still possible to alter the constant by using a non-constant pointer to the constant. However you have to make a conscious effort to override constant behaviour.
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What is new keyword in c?
enum, void and const are relatively new keywords in Cnew, on the other hand, isn't a keyword in C
What is the use of const keyword?
Marks constant data, ie data that should not be changed.
What keyword is used to declare a named constant?
Constant in Java refers to a fixed value that doesn’t change during the execution of a program. The value of constants appears right in a program. It is also known as Literals. We use the constants to create values that assign to variables. Constants can make our program easy to read and understood by others. Java does not directly support the constant. To define a variable as a constant, We use the “Static” and “Final” Keywords before declaring a variable. Hope this helps. Thank you
What is const pointer?
In computer science, const-correctness is the form of program correctness that deals with the proper declaration of objects as mutable or immutable. The term is mostly used in a C or C++ context, and takes its name from the const keyword in those languages. The idea of const-ness does not imply that the variable as it is stored in the computer's memory is unwriteable. Rather, const-ness is a compile-time construct that indicates what a programmer may do, not necessarily what he or she can do. In addition, a class method can be declared as const, indicating that calling that method does not change the object. Such const methods can only call other const methods but cannot assign member variables. (In C++, a member variable can be declared as mutable, indicating that a const method can change its value. Mutable member variables can be used for caching and reference counting, where the logical meaning of the object is unchanged, but the object is not physically constant since its bitwise representation may change.) In C++, all data types, including those defined by the user, can be declared const, and all objects should be unless they need to be modified. Such proactive use of const makes values "easier to understand, track, and reason about," and thus, it increases the readability and comprehensibility of code and makes working in teams and maintaining code simpler because it communicates something about a value's intended use. For simple data types, applying the const qualifier is straightforward. It can go on either side of the type for historical reasons (that is, const char foo = 'a'; is equivalent to char const foo = 'a';). On some implementations, using const on both sides of the type (for instance, const char const) generates a warning but not an error. For pointer and reference types, the syntax is slightly more subtle. A pointer object can be declared as a const pointer or a pointer to a const object (or both). A const pointer cannot be reassigned to point to a different object from the one it is initially assigned, but it can be used to modify the object that it points to (called the "pointee"). (Reference variables are thus an alternate syntax for const pointers.) A pointer to a const object, on the other hand, can be reassigned to point to another object of the same type or of a convertible type, but it cannot be used to modify any object. A const pointer to a const object can also be declared and can neither be used to modify the pointee nor be reassigned to point to another object. The following code illustrates these subtleties: void Foo( int * ptr, int const * ptrToConst, int * const constPtr, int const * const constPtrToConst ) { *ptr = 0; // OK: modifies the pointee ptr = 0; // OK: modifies the pointer *ptrToConst = 0; // Error! Cannot modify the pointee ptrToConst = 0; // OK: modifies the pointer *constPtr = 0; // OK: modifies the pointee constPtr = 0; // Error! Cannot modify the pointer *constPtrToConst = 0; // Error! Cannot modify the pointee constPtrToConst = 0; // Error! Cannot modify the pointer To render the syntax for pointers more comprehensible, a rule of thumb is to read the declaration from right to left. Thus, everything before the star can be identified as the pointee type and everything to after are the pointer properties. (For instance, in our example above, constPtrToConst can be read as a const pointer that refers to a const int.) References follow similar rules. A declaration of a const reference is redundant since references can never be made to refer to another object: int i = 42; int const & refToConst = i; // OK int & const constRef = i; // Error the "const" is redundant Even more complicated declarations can result when using multidimensional arrays and references (or pointers) to pointers. Generally speaking, these should be avoided or replaced with higher level structures because they are confusing and prone to error.
What is difference between constant in c plus plus and final in java?
The final keyword can be used to modify a class, method, or variable.When used on a variable, it means that variable cannot be changed once set.When used on a method, it means that no subclasses may override that method.
How do you declare a constant Explain it with a suitable example?
Declaring a Constant: We can declare a constant using the keyword "const". E.g. const abc='a';const number=10; const number[10]={1,2,3,4,5,6,7,8,9,10}; const name[7]={'K','U','N','D','A','N'}; #include<stdio.h> #include<conio.h> void main() { int i; const name[7]={'K','U','N','D','A','N'}; for(i=0;i<7;i++) { printf("%c",name[i]); getch(); }
What is new keyword in c?
enum, void and const are relatively new keywords in Cnew, on the other hand, isn't a keyword in C
What is the use of const keyword?
Marks constant data, ie data that should not be changed.
What is constant and readonly keyword in c?
It's 'const', example:const double pi = 3.1415926;
What keyword is used to declare a named constant?
Constant in Java refers to a fixed value that doesn’t change during the execution of a program. The value of constants appears right in a program. It is also known as Literals. We use the constants to create values that assign to variables. Constants can make our program easy to read and understood by others. Java does not directly support the constant. To define a variable as a constant, We use the “Static” and “Final” Keywords before declaring a variable. Hope this helps. Thank you
If you want to guarantee that the object remains the same after calling a member function on it how would you declare the function?
You would place the const keyword before the function body: class Object { public: Object():m_num(1){} int GetData() const; private: int m_num; }; int Object::GetData() const { return(m_num); } Since GetData() does not alter the instance, it makes sense to declare the function as constant. Note that class instance data members that are declared mutable can still be altered, regardless of constant functions. The use of constant functions only guarantees the non-mutable members cannot be altered.
Why does c do not accept the?
"the" is not a keyword in the C Programming Language. Perhaps you meant "const" HTH Richard Wolf Software Architect
What operator takes an object a reference or a pointer and returns a reference to global const object of type typeinfo?
The C++ typeid operator returns a const-qualified lvalue object of type std::type_info, as defined in the standard library header.
What is const pointer?
In computer science, const-correctness is the form of program correctness that deals with the proper declaration of objects as mutable or immutable. The term is mostly used in a C or C++ context, and takes its name from the const keyword in those languages. The idea of const-ness does not imply that the variable as it is stored in the computer's memory is unwriteable. Rather, const-ness is a compile-time construct that indicates what a programmer may do, not necessarily what he or she can do. In addition, a class method can be declared as const, indicating that calling that method does not change the object. Such const methods can only call other const methods but cannot assign member variables. (In C++, a member variable can be declared as mutable, indicating that a const method can change its value. Mutable member variables can be used for caching and reference counting, where the logical meaning of the object is unchanged, but the object is not physically constant since its bitwise representation may change.) In C++, all data types, including those defined by the user, can be declared const, and all objects should be unless they need to be modified. Such proactive use of const makes values "easier to understand, track, and reason about," and thus, it increases the readability and comprehensibility of code and makes working in teams and maintaining code simpler because it communicates something about a value's intended use. For simple data types, applying the const qualifier is straightforward. It can go on either side of the type for historical reasons (that is, const char foo = 'a'; is equivalent to char const foo = 'a';). On some implementations, using const on both sides of the type (for instance, const char const) generates a warning but not an error. For pointer and reference types, the syntax is slightly more subtle. A pointer object can be declared as a const pointer or a pointer to a const object (or both). A const pointer cannot be reassigned to point to a different object from the one it is initially assigned, but it can be used to modify the object that it points to (called the "pointee"). (Reference variables are thus an alternate syntax for const pointers.) A pointer to a const object, on the other hand, can be reassigned to point to another object of the same type or of a convertible type, but it cannot be used to modify any object. A const pointer to a const object can also be declared and can neither be used to modify the pointee nor be reassigned to point to another object. The following code illustrates these subtleties: void Foo( int * ptr, int const * ptrToConst, int * const constPtr, int const * const constPtrToConst ) { *ptr = 0; // OK: modifies the pointee ptr = 0; // OK: modifies the pointer *ptrToConst = 0; // Error! Cannot modify the pointee ptrToConst = 0; // OK: modifies the pointer *constPtr = 0; // OK: modifies the pointee constPtr = 0; // Error! Cannot modify the pointer *constPtrToConst = 0; // Error! Cannot modify the pointee constPtrToConst = 0; // Error! Cannot modify the pointer To render the syntax for pointers more comprehensible, a rule of thumb is to read the declaration from right to left. Thus, everything before the star can be identified as the pointee type and everything to after are the pointer properties. (For instance, in our example above, constPtrToConst can be read as a const pointer that refers to a const int.) References follow similar rules. A declaration of a const reference is redundant since references can never be made to refer to another object: int i = 42; int const & refToConst = i; // OK int & const constRef = i; // Error the "const" is redundant Even more complicated declarations can result when using multidimensional arrays and references (or pointers) to pointers. Generally speaking, these should be avoided or replaced with higher level structures because they are confusing and prone to error.
Write any two advantages of declaring a member function as const?
Immutable values are easier to understand, track, and reason about, so prefer constants over variables wherever it is sensible and make const your default choice when you define a value: It's safe, it's checked at compile time, and it's integrated with C++'s type system." The same applies to const member functions, which essentially just make the "this" pointer const.
What is difference between constant in c plus plus and final in java?
The final keyword can be used to modify a class, method, or variable.When used on a variable, it means that variable cannot be changed once set.When used on a method, it means that no subclasses may override that method.
Is it possible to delete a const object in C plus plus?
Yes. However, making a const pointer seems rather pointless, as you will be able to allocate and deallocate memory for it, but you will be unable to change the contents.
