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- Dictionaryuseful/ˈjuːsf(ʊ)l/
adjective
- 1. able to be used for a practical purpose or in several ways: "aspirins are useful for headaches" Similar Opposite
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2. #define is used to define some of the text substitutions performed by the preprocessor. If you write. and then refer to foo in your program, all instances of the identifier foo will be turned into the number 417. (But foo4 will remain as foo4, for instance.) then an occurrence of twice(417) in your program will turn into 417,417.
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.
Nov 27, 2015 · The most commonly used is probably WIN32_LEAN_AND_MEAN - it disables rarely used parts of the API. You can find more on MSDN's Using the Windows Headers. I remembered wrong about MSDN listing those defines, so here's list from windows.h: /* If defined, the following flags inhibit definition. * of the indicated items.
Nov 14, 2015 · 5. A short list of #define use guidelines for C++, points 2, 4, 6 and 7 actually address the question: Avoid them. Use them for the the common "include guard" pattern in header files. Otherwise, don't use them, unless you can explain, why you are using #define and not const, constexpr, or an inline or a template function, etc, instead.
Sep 3, 2008 · A tuple is a sequence of values. The values can be any type, and they are indexed by integer, so tuples are not like lists. The most important difference is that tuples are immutable. A tuple is a comma-separated list of values: t = 'p', 'q', 'r', 's', 't'. it is good practice to enclose tuples in parentheses:
I can't think of a reason why people shouldn't use it, when appropriate. It is useful in some circumstances, and not in others. I think that because it's an interesting technique, some coders perhaps end up using it more often than they should, without real justification. This has given recursion a bad name in some circles.
the substituted value need not be legal (or discrete) in the context where the #define is created, as it's evaluated at each point of use, so you can reference not-yet-declared objects, depend on "implementation" that needn't be pre-included, create "constants" such as { 1, 2 } that can be used to initialise arrays, or #define MICROSECONDS *1E-6 etc. (definitely not recommending this!)
Mar 28, 2018 · 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++ ...
I'm re-learning C++, and this time the resource i'm using mentions #define and #ifdef as if they are actually useful in the real world. The only remotely useful trick I am shown is this is this: #ifdef DEBUG #define Debug (x) x #else #define Debug (x) #endif. Which means I can do the following:
Jun 8, 2011 · 113. A multi-line macro is useful if you have a very complex macro which would be difficult to read if it were all on one line (although it's inadvisable to have very complex macros). In general, you can write a multi-line define using the line-continuation character, \. So e.g. #define MY_MACRO printf( \. "I like %d types of cheese\n", \.
