In other words, when the compiler starts building your code, no #define statements or anything like that is left. A good way to understand what the preprocessor does to your code is to get hold of the preprocessed output and look at it.
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.
Is it better to use static const variables than #define preprocessor? Or does it maybe depend on the context? What are advantages/disadvantages for each method?
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.
As far as I know, what you're trying to do (use if statement and then return a value from a macro) isn't possible in ISO C... but it is somewhat possible with statement expressions (GNU extension). Since #define s are essentially just fancy text find-and-replace, you have to be really careful about how they're expanded. I've found that this works on gcc and clang by default:
2 #define is a preprocessor operation and will cause all occurrences of m to be replaced by 30000 before the compilation phase happens. The other two examples are bona fide variables. The static variable exists in the translation unit in which it is declared and can be modified. The const variable is read-only.
So I read the interesting answers about what are the differences between constexpr and const but I was curious about are the differences between #define and constexpr ? I feel like constexpr is jus...
#define simply substitutes a name with its value. Furthermore, a #define 'd constant may be used in the preprocessor: you can use it with #ifdef to do conditional compilation based on its value, or use the stringizing operator # to get a string with its value.
