In other words, when the compiler starts building your code, no #define statements or anything like that is left Still, it is something to keep in. A good way to understand what the preprocessor does to your code is to get hold of the preprocessed output and look at it.
What is the point of #define in c++ Clearly this is a corner case and probably doesn't matter considering how width will presumably be used 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.
I've found that this works on gcc and clang by default: How can i use #if inside #define in the c preprocessor Asked 15 years, 7 months ago modified 8 months ago viewed 51k times #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. 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.
[duplicate] asked 12 years, 6 months ago modified 2 years, 11 months ago viewed 241k times The #define directive is a preprocessor directive The preprocessor replaces those macros by their body before the compiler even sees it Think of it as an automatic search and replace of your source code
A const variable declaration declares an actual variable in the language, which you can use.well, like a real variable Take its address, pass it around, use it, cast/convert it, etc #define _add_penguin(a) penguin ## a #define add_penguin(a) _add_penguin(a) #define width (100) #define height 200 add_penguin(height) // expands to penguin200 add_penguin(width) // error, cannot concatenate penguin and (100) same for stringization (#)
