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Similarly, a variable CPPFLAGS exists with switches to be passed to the C or C++ preprocessor. Similarly, FFLAGS enables the addition of switches for a Fortran compiler. These variables are most commonly used to specify optimization or debugging switches to a compiler, as for example -g , -O2 or ( GCC -specific) -march=athlon .
Class templates are really meta-classes: they are partial abstract data types that provide instructions to the compiler on how to create classes with the proper data members. For example, the C++ standard containers are class templates. When a programmer uses a vector, one instantiates it with a specific data type, for example, int, string or ...
The curiously recurring template pattern (CRTP) is an idiom, originally in C++, in which a class X derives from a class template instantiation using X itself as a template argument. [1] More generally it is known as F-bound polymorphism , and it is a form of F -bounded quantification .
Macros are usually referred to as variables when they hold simple string definitions, like CC = clang. Macros in makefiles may be overridden in the command-line arguments passed to the Make utility. Environment variables are also available as macros. For example, the macro CC is frequently used in makefiles to refer to the location of a C ...
Another example of how a class implementation file would be structured can be seen with Objective-C, which is used in iOS programming. [13] This example will use "ExampleClass". A notable difference between C++ and Objective-C when making use of these implementation files is the extensions used at the end of the files.
For example, a portable library can not define an allocator type that will pull memory from different pools using different allocator objects of that type. (Meyers, p. 50) (addressed in C++11). The set of algorithms is not complete: for example, the copy_if algorithm was left out, [13] though it has been added in C++11. [14]
Presented below is a simple (contrived) example of a C++ hello world program, where the text to be printed and the method of printing it are decomposed using policies.In this example, HelloWorld is a host class where it takes two policies, one for specifying how a message should be shown and the other for the actual message being printed.
The std::string class is the standard representation for a text string since C++98. The class provides some typical string operations like comparison, concatenation, find and replace, and a function for obtaining substrings. An std::string can be constructed from a C-style string, and a C-style string can also be obtained from one. [7]