Can you forward declare enum?
There is indeed no such thing as a forward declaration of enum. As an enum’s definition doesn’t contain any code that could depend on other code using the enum, it’s usually not a problem to define the enum completely when you’re first declaring it.
Can typedef be used with enum?
typedef can be used to rename any data type including enum and struct definitions, which we will study shortly. The typedef statement may be specified by itself or as part of a enum or struct definition. The typedef defined new name is often the given the same name as the enum or struct definition.
What is the size of enum variable?
The size is four bytes because the enum is stored as an int . With only 12 values, you really only need 4 bits, but 32 bit machines process 32 bit quantities more efficiently than smaller quantities. Without enums, you might be tempted to use raw integers to represent the months.
How big should an enum be?
On an 8-bit processor, enums can be 16-bits wide. On a 32-bit processor they can be 32-bits wide or more or less. The GCC C compiler will allocate enough memory for an enum to hold any of the values that you have declared. So, if your code only uses values below 256, your enum should be 8 bits wide.
How do I forward a declared nested class?
You cannot forward declare a nested structure outside the container. You can only forward declare it within the container. Create a common base class that can be both used in the function and implemented by the nested class.
Why do we need forward declaration in C++?
A forward declaration tells the compiler about the existence of an entity before actually defining the entity. Forward declarations can also be used with other entity in C++, such as functions, variables and user-defined types.
What is typedef example?
typedef struct { int scruples; int drams; int grains; } WEIGHT; The structure WEIGHT can then be used in the following declarations: WEIGHT chicken, cow, horse, whale; In the following example, the type of yds is “pointer to function with no parameter specified, returning int “.
What is typedef and enum in C?
There are two different things going on there: a typedef and an enumerated type (an “enum”). A typedef is a mechanism for declaring an alternative name for a type. An enumerated type is an integer type with an associated set of symbolic constants representing the valid values of that type.
How do you find the enum size?
values() method to get an array of Enum values then use the length property. The Enum. values() returns an array of all the enum constants. You can use the length variable of this array to get the number of enum constants.
Is enum a data type?
Enumeration (or enum) is a user defined data type in C. It is mainly used to assign names to integral constants, the names make a program easy to read and maintain. The keyword ‘enum’ is used to declare new enumeration types in C and C++.
What is a nested class C++?
Nested Classes in C++ A nested class is a class which is declared in another enclosing class. A nested class is a member and as such has the same access rights as any other member. The members of an enclosing class have no special access to members of a nested class; the usual access rules shall be obeyed.
Can we create nested classes in C++ True or false?
Nested Classes in C++ A nested class is a class that is declared in another class. The nested class is also a member variable of the enclosing class and has the same access rights as the other members. A program that demonstrates nested classes in C++ is as follows.
Why is it not standard to forward declare enums?
Forward declaring enums is non-standard, because pointers to different enum types are not guaranteed to be the same size. The compiler may need to see the definition to know what size pointers can be used with this type. In practice, at least on all the popular compilers, pointers to enums are a consistent size.
How do you name an enum in typedef?
There are several possibilities and conventions to name an enumeration. The first is to use a tag name just after the enum keyword. This enumeration must then always be used with the keyword and the tag like this: If we use typedef directly when declaring the enum, we can omit the tag name and then use the type without the enum keyword:
When to use forward declaration of Type Identifier?
However, the size of a pointer or reference is known to the compiler, regardless of the size of the pointee, so a forward declaration is sufficient – it declares a type identifier name.
When to forward declare a type in C + +?
Interestingly, when using pointer or reference to class or struct types, the compiler can handle incomplete types saving you the need to forward declare the pointee types as well: // header.h // Look Ma!
