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- Is it possible to use a if statement inside #define?
There are multiple problems with your macro: it expands to a statement, so you cannot use it as an expression the arguments are not properly parenthesized in the expansion: invoking this macro with anything but variable names or constants will produce problems the arguments are evaluated multiple times: if you invoke the macro with arguments that have side effects, such as SUM_A(a(), b()) or
- How do I declare a global variable in VBA? - Stack Overflow
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- Why use #define instead of a variable - Stack Overflow
What is the point of #define in C++? I've only seen examples where it's used in place of a "magic number" but I don't see the point in just giving that value to a variable instead
- How do I show the value of a #define at compile-time?
I know that this is a long time after the original query, but this may still be useful This can be done in GCC using the stringify operator "#", but it requires two additional stages to be defined first #define XSTR(x) STR(x) #define STR(x) #x The value of a macro can then be displayed with: #pragma message "The value of ABC: " XSTR(ABC) See: 3 4 Stringification in the gcc online
- What is the purpose of the #define directive in C++?
0 in C or C++ #define allows you to create preprocessor Macros In the normal C or C++ build process the first thing that happens is that the PreProcessor runs, the preprocessor looks though the source files for preprocessor directives like #define or #include and then performs simple operations with them
- Why are #ifndef and #define used in C++ header files?
I have been seeing code like this usually in the start of header files: #ifndef HEADERFILE_H #define HEADERFILE_H And at the end of the file is #endif What is the purpose of this?
- c++ - Declaring a function using #define - Stack Overflow
The #define version is still a macro The code is expanded at the invocation site It has all the expected problems (with macros) including namespace pollution and unexpected parameter behaviour
- Is there a way to do a #define inside of another #define?
You could for example do an ifdef guard to initialize a variable in a macro but make sure it isn't declared twice I'm sure there are other possible use cases Besides, it's normal to give simplified examples when asking theoretical questions Pointing out there's a different way is kind of pointless for this kind of question
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