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- What is the purpose of the #define directive in C++?
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 in the case of a #define directive the preprocessor does simple text based substitution
- c++ - Why use #define instead of a variable - Stack Overflow
Most compilers will allow you to define a macro from the command line (e g g++ -DDEBUG something cpp), but you can also just put a define in your code like so: #define DEBUG Some resources: Wikipedia article; C++ specific site; Documentation on GCC's preprocessor; Microsoft reference; C specific site (I don't think it's different from the C++
- c++ - What does ## in a #define mean? - Stack Overflow
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
- Is it possible to use a if statement inside #define?
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)
- c++ - static const vs. #define - Stack Overflow
#define is a compiler pre processor directive and should be used as such, for conditional compilation etc E g where low level code needs to define some possible alternative data structures for portability to specif hardware It can produce inconsistent results depending on the order your modules are compiled and linked
- Why do most C developers use define instead of const?
#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 And as the compiler knows its value at compile time it may optimize code based on that
- c# - Define #define, including some examples - Stack Overflow
#define is a special "before compile" directive in C# (it derives from the old C preprocessor directives) that defines a preprocessor symbol Coupled with #if , depending on what symbols are defined, the various code will be effectively commented out
- What is the difference between #define and const? [duplicate]
DEFINE is a preprocessor instruction (for example, #define x 5) The compiler takes this value and inserts it wherever you are calling x in the program and generate the object file "Define" constants don't create a symbol entry in symbol table If you wanted to debug the program, you would not find x Use constant where ever possible that what
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