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How would you declare a constant of 5 called MYCONST?
A constant of 5 called MYCONST would be declared as #define MYCONST 5. This is because the statement used is a define statement.
How string constants are declared in c?
Some strings are constants, others aren't; some constants are strings, other aren't. So these are unrelated things. Examples: "text" -- constant string 123 -- constant number char s[40] -- variable string
What is a constant member function c plus plus?
A constant member function is an instance method that can only modify the mutable members of the class instance. This is achieved by implicitly declaring the this pointer constant. The this pointer is a hidden parameter that is implicitly passed to every instance function, and that points to the current instance of the class. Static member functions do not have an implicit this pointer and therefore cannot be declared const. Consider the following simple class that has both mutable and non-mutable member variables, and both constant and nonconstant member functions: struct foo { void constant()const; void nonconstant(); private: int data1; mutable int data2; }; void foo::constant()const { data1++; // not permitted: the implicit this pointer is declared const data2++; // ok: data2 is mutable } void foo::nonconstant() { data1++; // ok: the implicit this pointer is declared non-const data2++; // ok: data2 is mutable } Note that data2 can always be modified since it is declared mutable, but data1 can only be modified by nonconstant member functions. Members should only be declared mutable when they are only used internally by a class (such as when locking a mutex for thread safety), or where a value needs to be calculated and cached the first time it is accessed.
How can you change the value of a constant variable in C?
You can change a static variable by putting the static variable into a function that has operations that you intend to execute upon the variable. Example, you want to change the static variable to another value or make an addition of 2. Put the source code inside a function with the static variable declared locally within the function.Every time you call the function, the static variable value will change. Take note that the static variable retains the last value you declared it in your function call.A more terse answerLocal variables declared as static are changed as normal; they are special in that their values persist across function calls.
Which access specifier is preferred for constant variables?
There's no such thing as a constant variable (other than as an oxymoron). A named value is either declared constant or it is declared variable, it cannot be both a constant and a variable.You declare a constant much as you would a variable, except you use the final keyword modifier and name the constant using ALL CAPS and underscores for spaces.final int HOURS_IN_DAY = 24;final int DAYS_IN_WEEK;DAYS_IN_WEEK = 7;Note that we don't need to assign a constant value at the point of instantiation. However, once assigned we cannot then change the value. It wouldn't be a constant if we could!The preferred access specifier depends on how useful the constant is. If only one method makes use of the constant, then it should simply be declared within that method as a local constant. If several methods of the same class make use of the constant then declare it a private member of the class. Both methods are used in the following example:public class MyClass {private static int HOURS_IN_DAY = 24;public int hoursInDays (int days) {return days * HOURS_IN_DAY;}public int hoursInWeeks (int weeks) {final int DAYS_IN_WEEK = 7;return weeks * DAYS_IN_WEEK * HOURS_IN_DAY;}}Note the use of the static keyword in the constant declaration. It doesn't make sense for every object of a class to store independent copies of the same constant value, thus we must declare class constants as static members so that all objects of the class can share the same instance of the constant and thus share the same value.If we want the constant to be accessible to our subclasses, then we can declare the constant protected. If we want to make the constant available outside of the class then we can declare it public.Keep in mind that although constants are not variable, we should only expose what needs to be exposed outside of a class, no more and no less. A constant that provides a class implementation detail has no business being accessible outside of the class in which it is declared.You should also be aware that the rules governing constants are different for primitive data types and objects. With primitive data types, the value is constant as one would expect. But with objects, only the reference is constant (we cannot refer to a different object) but if the referenced object allows mutations then it is not truly constant. Unfortunately, the only way to create a truly constant object from a mutable class is to subclass the mutable class and render its setters private.
What is the constant in C programming language?
Anything declared as a constant.
How would you declare a constant of 5 called MYCONST?
A constant of 5 called MYCONST would be declared as #define MYCONST 5. This is because the statement used is a define statement.
What are the differences of a constant and a variable?
A constant has only the exact value it's declared and can never be changed. A variable can have any number of values assigned. In programming, a variable can be given a value later in the code but can only be changed during runtime if its been declared as a pointer.
Example of constant and variables?
Variables are values that can change during the program once declared. Oppose to that, Constants, also values once declared, can't change their values.
Einstein used the cosmological constant in his general relativity equations to do what?
Einstein used approximation methods in working out initial predictions of the theory. Einstein later declared the cosmological constant the biggest blunder of his life.
What is static variable and how it is declared?
static variables are declared to define a variable as a constant., means if you declare a variable as static the variable becomes costant.syntaxstatic int a=100;this will make the value of a as 100 which is not to be changedWell, no; you think of 'const', which can be used together with static, but not necessarily.Yes you are right bro I was confused it should be const int a=100; then the variable will be a constant.
How can you change values in call by reference?
We don't call by reference, we call functions. The arguments passed to the function are passed (not called) either by value or by reference, depending upon the function signature (the prototype). When you pass by reference you are passing the actual variable, not a copy of the variable, thus the function can modify that variable's value directly. The only exception is when the parameter is declared a constant reference. Passing a pointer is essentially the same as passing by reference, however the pointer itself is passed by value. To pass a pointer by reference you must pass a pointer-to-pointer instead. Passing by value always copies the value, whether it is declared constant or not. But if it is declared constant, the function might as well accept a constant reference. Passing objects (instances of a class) by constant value will incur a performance penalty in making an unnecessary copy. If it is constant, there is little point in copying the object.
How string constants are declared in c?
Some strings are constants, others aren't; some constants are strings, other aren't. So these are unrelated things. Examples: "text" -- constant string 123 -- constant number char s[40] -- variable string
What is a constant member function c plus plus?
A constant member function is an instance method that can only modify the mutable members of the class instance. This is achieved by implicitly declaring the this pointer constant. The this pointer is a hidden parameter that is implicitly passed to every instance function, and that points to the current instance of the class. Static member functions do not have an implicit this pointer and therefore cannot be declared const. Consider the following simple class that has both mutable and non-mutable member variables, and both constant and nonconstant member functions: struct foo { void constant()const; void nonconstant(); private: int data1; mutable int data2; }; void foo::constant()const { data1++; // not permitted: the implicit this pointer is declared const data2++; // ok: data2 is mutable } void foo::nonconstant() { data1++; // ok: the implicit this pointer is declared non-const data2++; // ok: data2 is mutable } Note that data2 can always be modified since it is declared mutable, but data1 can only be modified by nonconstant member functions. Members should only be declared mutable when they are only used internally by a class (such as when locking a mutex for thread safety), or where a value needs to be calculated and cached the first time it is accessed.
How do you declare a constant using PHP?
Outside of a class definition, constants can be declared with the define function. The function has two arguments; the name of the constant (a string), and the value of the constant (any variable type).Inside a class definition, constants can be declared with the const keyword. Type the word const, the name of the constant in the form of how it will be called later, an "equals sign," then the desired value of the constant.In both cases, here is an example.
Can constructor be declared as constant in c plus plus?
No. Constructors initialise objects and, by definition, must be able to modify the member variables. Uninitialised members are a disaster waiting to happen even without a constructor declared const! Thankfully, the compiler won't permit a const constructor.
How can you change the value of a constant variable in C?
You can change a static variable by putting the static variable into a function that has operations that you intend to execute upon the variable. Example, you want to change the static variable to another value or make an addition of 2. Put the source code inside a function with the static variable declared locally within the function.Every time you call the function, the static variable value will change. Take note that the static variable retains the last value you declared it in your function call.A more terse answerLocal variables declared as static are changed as normal; they are special in that their values persist across function calls.
