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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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May 15, 2011 · 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.
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.
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.
Jul 25, 2019 · 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 ...
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.
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 28, 2009 · #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.
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.
Apr 2, 2012 · 1. I added a line below the code saying you should add the symbols from the build tab of project properties: Conditional compilation Symbols. – ionden. Apr 2, 2012 at 7:44. -1 this is an example of #if/#else - the question asks for a real world example of #define. – MattDavey.
Jun 23, 2009 · In the programming world, polymorphism is used to make applications more modular and extensible. Instead of messy conditional statements describing different courses of action, you create interchangeable objects that you select based on your needs. That is the basic goal of polymorphism. edited Oct 13, 2016 at 13:17.
