That's possible for sure, but this seriously sounds like an XY Problem. Are Bar and Macro different macros? And do you want the Macro macro to be called for each call expansion of the variadic template? Thanks for your advice.
Although I were not agree with you completely, but I changed the question to avoid to look an XY problem. They are different and the Macro must call for each version.
MohsenTamiz I think this slight variation makes a little more sense. Show 3 more comments. Active Oldest Votes. This result is put inside a couple of parentheses. Improve this answer. Add a comment. I think that this now does what you want: define BAR RobClucas RobClucas 5 5 silver badges 16 16 bronze badges. May be I must tell more about Macro , it is another macro that I have to use.
Library data types, whether an array , list , sequence , or tuple , have a rich set of functionality for manipulating data whereas variadic data functionality in the library only allows one to access the variadic data as a whole or to access a single token of the variadic data at a time.
The user of the library still may choose to pass variadic data back into internal macros rather than convert it to other library data types. There is no problem passing variadic data as a whole to variadic macros as the last parameter of the macro. However: Attempting to pass variadic data as a whole directly into a non-variadic macro is not guaranteed to work and may fail.
What follows are very simple examples, showing how variadic data can be passed to a non-variadic macro. First an example of what NOT to do. There are two ways to pass variadic data to a non-variadic macro. This macro allows one to "overload" a variadic macro to non-variadic macros of different numbers of parameters, using a common prefix. Visitation of a variant requires a visitor object.
With the implementation of the above visitor, we can then apply it to v , as seen in the following:. As expected, the content of v is now a std::string equal to "hello world! We'll skip the verification this time. In addition to enhanced robustness, visitation provides another important advantage over get : the ability to write generic visitors. While the initial setup costs of visitation may exceed that required for get , the benefits quickly become significant.
This behavior is particularly useful when operating on sequences of variant type, as the following demonstrates:. This section discusses several features of the library often required for advanced uses of variant. Unlike in the above section, each feature presented below is largely independent of the others. Accordingly, this section is not necessarily intended to be read linearly or in its entirety. While the variant class template's variadic parameter list greatly simplifies use for specific instantiations of the template, it significantly complicates use for generic instantiations.
This macro simplifies for the user the process of declaring variant types in function templates or explicit partial specializations of class templates, as shown in the following:.
While convenient for typical uses, the variant class template's variadic template parameter list is limiting in two significant dimensions. Second, the nature of parameter lists in general makes compile-time manipulation of the lists excessively difficult. Run this code. Hello world! Category : Todo with reason.
Compiler support. Freestanding and hosted. Language support library. Technical specifications. Flow control. Function declaration. Lambda function expression. Fundamental types. Function types. Compound types. Storage duration specifiers. Default initialization.
Value initialization. Zero initialization. Copy initialization. Direct initialization. Aggregate initialization. Constant initialization.
Reference initialization. Value categories. Order of evaluation. Operator precedence.
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