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- Dictionaryused/yo͞ozd/
adjective
- 1. having already been used: "scrawling on the back of a used envelope"
- 2. secondhand: "a used car"
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Nov 27, 2015 · The #define directive has two common uses. The first one, is control how the compiler will act. To do this, we also need #undef, #ifdef and #ifndef. (and #endif too...) You can make "compiler logic" this way. A common use is to activate or not a debug portion of the code, like that: #ifdef DEBUG. //debug code here.
Mar 28, 2018 · So if you used a variable instead of a #define, you had no guarantee that somebody somewhere wouldn't change the value of it, causing havoc throughout your program. In the old days, FORTRAN passed even constants to subroutines by reference, and it was possible (and headache inducing) to change the value of a constant like '2' to be something different.
Mar 4, 2017 · 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 value. For example: #define SCALE 1 ...
Oct 30, 2013 · 14. In C# #define macros, like some of Bernard's examples, are not allowed. The only common use of #define / #if s in C# is for adding optional debug only code. For example: static void Main(string[] args) //this only compiles if in DEBUG. Console.WriteLine("DEBUG") //this only compiles if not in DEBUG.
3. #ifndef checks whether the given token has been #defined earlier in the file or in an included file; if not, it includes the code between it and the closing #else or, if no #else is present, #endif statement. #ifndef is often used to make header files idempotent by defining a token once the file has been included and checking that the token ...
One technique I've used for the declare/define issue is to conditionally define GLOBAL as extern or nothing at the top of the header and then declare variables as GLOBAL struct a myAValue;. From most source files, you arrange for the #define GLOBAL extern version to be used ( declaring the variables) and from exactly one source file it causes the empty define to be used so the variables are ...
Apr 27, 2023 · 53. #define has many different applications, but your question seems to be about one specific application: defining named constants. In C++ there's rarely a reason to use #define to define named constants. #define is normally widely used in C code, since C language is significantly different from C++ when it comes to defining constants.
Oct 17, 2022 · The clean, reliable way to declare and define global variables is to use a header file to contain an extern declaration of the variable. The header is included by the one source file that defines the variable and by all the source files that reference the variable. For each program, one source file (and only one source file) defines the variable.
It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino and Node. Using a modular script loader like RequireJS will improve the speed and quality of your code.
I'm trying to make a macro with the following formula: (a^2/(a+b))*b, and I want to make sure that the there will be no dividing by zero.
