Nature: A Dictionary of Scientific Terms: Pronunciation, Derivation, and Definition of Terms in Biology, Botany, Zoology, Anatomy, Cytology, Embryology, Physiology A Dictionary of Scientific Terms: Pronunciation, Derivation, and Definition of Terms in Biology, Botany, Zoology, Anatomy, Cytology, Embryology, Physiology 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. c++ - Why use #define instead of a variable - Stack Overflow 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. Oh ...
define cytology, The question is if users can define new macros in a macro, not if they can use macros in macros. 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: I know that this is a long time after the original query, but this may still be useful.
define cytology, 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 ...
