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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)
- 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++
- How can I use #if inside #define in the C preprocessor?
#ifdef USE_CONST #define MYCONST const #else #define MYCONST #endif Then you can write code like this: MYCONST int x = 1; MYCONST char* foo = "bar"; and if you compile with USE_CONST defined (e g , typically something -DUSE_CONST in the makefile or compiler options) then it will use the consts; otherwise it won't
- 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
- 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++ - 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
- Explicitly Define Datatype in Python Function - Stack Overflow
You could indeed perform those check, at the cost of increased volume and complexity of code The pythonic way is to assume the happy path (all types correct) is being followed, and cross the bridge of handling any errors when they become obvious (i e when the code raises an exception)
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