What is __ Va_args __ C++?
Preprocessor: __VA_ARGS__ (Variadic macros) If the parameters of a macro contain three consecutive dots ( ), this indicates that an arbitrary number of parameters may be passed. In the macro expansion, these values that are then referenced by the special identifier __VA_ARGS__ .
Where is __ Va_args __ defined?
Or with any number of arguments. The __VA_ARGS__ refers back again to the variable arguments in the macro itself. Show activity on this post. When the macro is invoked, all the tokens in its argument list […], including any commas, become the variable argument.
What is #__ Va_args __?
16.3. An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it were a parameter, and the variable arguments shall form the preprocessing tokens used to replace it. this is the same for varags as it is for normal parameters.
What type is __ Va_args __?
To use variadic macros, the ellipsis may be specified as the final formal argument in a macro definition, and the replacement identifier __VA_ARGS__ may be used in the definition to insert the extra arguments. __VA_ARGS__ is replaced by all of the arguments that match the ellipsis, including commas between them.
What are C++ macros?
Macros and its types in C/C++ A macro is a piece of code in a program that is replaced by the value of the macro. Macro is defined by #define directive. Whenever a macro name is encountered by the compiler, it replaces the name with the definition of the macro.
Can macro return a value?
Macros just perform textual substitution. They can’t return anything – they are not functions.
Is argv a pointer?
The first element of the array, argv , is a pointer to the character array that contains the program name or invocation name of the program that is being run from the command line. argv indicates the first argument passed to the program, argv the second argument, and so on.
Are macros good in C++?
So, macros are always useful because they are outside the normal compiler rules. But I find that most the time I see one, they are effectively remains of C code never translated into proper C++. Use the CPP only for what the compiler cannot do.
How do I create a macro in C++?
The naïve way to write the macro is like this: #define MACRO(X,Y) \ cout << “1st arg is:” << (X) << endl; \ cout << “2nd arg is:” << (Y) << endl; \ cout << “Sum is:” << ((X)+(Y)) << endl; This is a very bad solution which fails all three examples, and I shouldn’t need to explain why.
What is ## in macro in C?
Token-pasting operator (##) Allows tokens used as actual arguments to be concatenated to form other tokens. It is often useful to merge two tokens into one while expanding macros. This is called token pasting or token concatenation. The ‘##’ pre-processing operator performs token pasting.
What does =+ mean in C++?
The statement that =+ is assignment (equivalent to plain = operator), while += increases a variable’s value by a certain amount, is INCORRECT. x += y as well as x =+ y will BOTH have the same effect (that is, both of these will cause the new value of x to be the old value of x + y).