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- Dictionaryuse·ful/ˈyo͞osf(ə)l/
adjective
- 1. able to be used for a practical purpose or in several ways: "aspirin is useful for headaches" Similar Opposite
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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.
What is #define useful for? Why use constants instead of variables? The answers to which are: #define can do more complicated things then just replace a number with a name. It can actually take parameters. For example: #define getmax(a,b) a>b?a:b does not merely replace a number with a name.
May 15, 2011 · 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++ ...
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 ...
Nov 27, 2015 · The most common use (by far) of #define is for include guards: // header.hh #ifndef HEADER_HH_ #define HEADER_HH_ namespace pony { // ... } #endif Another common use of #define is in creating a configuration file, commonly a config.h file, where we #define macros based on various states and conditions.
Nov 27, 2015 · In one of the answers to this question jalf spoke about useful define NOMINMAX, that could prevent from unwanted defining min/max macros. Are there other useful defines that can help to control windows.h (or other Windows headers, for instance Microsoft C Runtime headers or STL implementation) behavior?
Sep 3, 2008 · For example, suppose you have an object that passes out an opaque cookie to a caller from one method which is then passed into another method. A tuple is a good way to pack multiple values into that cookie without having to define a separate class to contain them. I try to be judicious about this particular use, though.
Nov 14, 2015 · For some uses of #define macros, this means #define just before a function in .cpp file, then #undef right after the function. The exact use case for #define determines if it should be in .h or in .cpp file. But note that most use cases are actually in violation of 3. above, and you should actually not use #define.
Mar 17, 2009 · I can understand the need to define different build types for debug or cross platform builds in the preprocessor but the ability to define arbitrary substitutions seems to be useful only to make an already difficult language even more difficult to understand. Why was such a complex preprocessor introduced for C?
Jun 23, 2009 · For example, you can define a generic "list" template class, and then instantiate it as "list of integers", "list of strings", maybe even "list of lists of strings" or the like. Generally, you write the code once for a data structure of arbitrary element type, and the compiler generates versions of it for the various element types.
