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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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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++ ...
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.
Recursion is solving a problem with a function that calls itself. A good example of this is a factorial function. Factorial is a math problem where factorial of 5, for example, is 5 * 4 * 3 * 2 * 1. This function solves this in C# for positive integers (not tested - there may be a bug).
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 ...
Sep 9, 2014 · 1. A tuple is useful for storing multiple values.. As you note a tuple is just like a list that is immutable - e.g. once created you cannot add/remove/swap elements. One benefit of being immutable is that because the tuple is fixed size it allows the run-time to perform certain optimizations.
Oct 2, 2011 · A lambda is an unnamed function that is useful (in actual programming, not theory) for short snippets of code that are impossible to reuse and are not worth naming. In C++, the minimal lambda expression looks like: []{} // lambda with no parameters that does nothing. [] is the capture list and {} the function body.
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.
The macro you posted from GCC (min and max) is an example of this, they use the global variables _a and _b to avoid the risk of double evaluation (like in max(x++,y++)) (well, they use GCC extensions but the concept is the same). I like using macros where it helps to make things more clear but they are a sharp tool!
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 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.
