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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 - #Define VS Variable - Stack Overflow
The scope of #define is limited to the file in which it is defined So, #defines which are created in one source file are NOT available in a different source file In short, #defines don't respect scopes Note that const variables can be scoped They obey all scoping rules
- 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# - How do you use #define? - Stack Overflow
#define is used to define compile-time constants that you can use with #if to include or exclude bits of code #define USEFOREACH #if USEFOREACH foreach(var item in items) { #else for(int i=0; i < items Length; ++i) { var item = items[i]; take item #endif doSomethingWithItem(item); }
- 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
- c++ - const string vs. #define - Stack Overflow
i need to share some strings in my c++ program should i use #define or const string? thanks mystring1 h #define str1 "str1" #define str2 "str2" Or mystring2 h extern const string str1;
- 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
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