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- c++ - Why use #define instead of a variable - Stack Overflow
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# - How do you use #define? - Stack Overflow
8 #define is used to define compile-time constants that you can use with #if to include or exclude bits of code
- 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) 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:
- 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
- How can I use #if inside #define in the C preprocessor?
Just do something like this: #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
- What is the difference between #define and const? [duplicate]
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
- c preprocessor - Is there a good reason for always enclosing a define . . .
#define _add_penguin(a) penguin ## a #define add_penguin(a) _add_penguin(a) #define WIDTH (100) #define HEIGHT 200 add_penguin(HEIGHT) expands to penguin200 add_penguin(WIDTH) error, cannot concatenate penguin and (100) Same for stringization (#) Clearly this is a corner case and probably doesn't matter considering how WIDTH will presumably be used Still, it is something to keep in
- How can I define a define in C? - Stack Overflow
The question is if users can define new macros in a macro, not if they can use macros in macros
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