Which of the following is not recommended in a header file
A. type definitions (typedefs)
B. class definitions
C. function definitions
D. template definitions
Answer» D. template definitions
The correct answer is D. template definitions. In a header file, it is generally not recommended to include template definitions.
Header files are used to declare the interfaces and provide forward declarations for functions, classes, and types that will be used in a program. They are typically included in multiple source files and serve as a way to share declarations and definitions across different compilation units.
Template definitions, on the other hand, are typically implemented in the same file where they are used. Templates are a way to define generic types and functions that can be instantiated with different types at compile time. The implementation of a template often requires including additional code, which can lead to code bloat and longer compilation times.
When template definitions are included in a header file, every source file that includes that header will have a copy of the template code. This can result in multiple definitions of the same template, leading to linker errors due to duplicate symbols.
To avoid these issues, it is recommended to separate the implementation of template functions and classes into a separate implementation file (usually with a .cpp extension) and provide only the declarations and forward declarations in the header file. This way, the template definitions are only compiled once, reducing code duplication and potential linker errors.
Now let’s explain why the other options (A, B, and C) are incorrect in separate paragraphs:
A. Type definitions (typedefs) are commonly included in header files. Typedefs are used to create aliases for existing types, which can improve code readability and maintainability. Including type definitions in a header file allows other source files to use those aliases without the need to redefine them.
B. Class definitions are often included in header files. When a class is declared in a header file, other source files can use objects of that class and call its member functions. By including the class definition in a header file, the class interface becomes accessible to other parts of the program.
C. Function definitions, also known as inline functions, can be included in header files. Inline functions are small functions that are expanded by the compiler at the call site, eliminating the overhead of function calls. Including function definitions in a header file allows the compiler to inline the function wherever it is used, potentially improving performance.
However, it is worth noting that large or complex functions are not suitable for inlining, and including their definitions in header files can lead to code bloat.
In summary, template definitions are not recommended in header files due to potential code duplication and linker errors. However, type definitions, class definitions, and function definitions are commonly included in header files to provide interfaces and declarations for other parts of the program.
MBA,BBA.
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I hold a MBA degree from Presidential Business School, Kathmandu, and a BBA degree with a specialization in Finance from Apex College,