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3 Example. 4 See also. 5 ... The C date and time functions are a group of functions in the standard library of the C programming language ... added to C++ in 2020 in ...
C++14 relaxes the constraints on constexpr – allowing local declarations and use of conditionals and loops (the general restriction that all data required for the execution be available at compile-time remains). Here's an example of compile-time function evaluation in C++14:
In C++ templates, compile-time cases were historically performed by pattern matching over the template arguments. For example, the template base class in the Factorial example below is implemented by matching 0 rather than with an inequality test, which was previously unavailable.
When he started with C++, he finally found a language where it was possible to create generic algorithms (e.g., STL sort) that perform even better than, for example, the C standard library qsort, thanks to C++ features like using inlining and compile-time binding instead of function pointers.
In the GCC, the pure attribute specifies property 2, while the const attribute specifies a truly pure function with both properties. [9] Languages offering compile-time function execution may require functions to be pure, sometimes with the addition of some other constraints. Examples include constexpr of C++ (both properties). [10]
A built-in function, or builtin function, or intrinsic function, is a function for which the compiler generates code at compile time or provides in a way other than for other functions. [23] A built-in function does not need to be defined like other functions since it is built in to the programming language. [24]
What exactly "programming at compile-time" means can be illustrated with an example of a factorial function, which in non-template C++ can be written using recursion as follows: unsigned factorial ( unsigned n ) { return n == 0 ? 1 : n * factorial ( n - 1 ); } // Usage examples: // factorial(0) would yield 1; // factorial(4) would yield 24.
The C standard library, sometimes referred to as libc, [1] is the standard library for the C programming language, as specified in the ISO C standard. [2] Starting from the original ANSI C standard, it was developed at the same time as the C POSIX library, which is a superset of it. [3]