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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
- 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)
- Difference between `constexpr` and `#define` - Stack Overflow
Statements defined using #define are called macros And macros are used in a multitude of uses We can use them to conditionally compile sections of code #ifdef ONE int AddOne(int x) { return x + 1; } #else int AddTwo(int x) { return x + 2; } #endif When we don't need to store constants in a variable #define MAX_BOUND 1000 #define MIN_BOUND 10
- 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
- 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
- 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
- How do I define a function with optional arguments?
These two aren't equivalent: * In the first example, 'b' is still a positional argument that must be provided: * in the second example, 'b' is a true optional argument that can be ommitted (and in this case will have the value None if ommitted)
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