C mathematical functions

Most of the mathematical functions, which use floating-point numbers, are defined in ( header in C++). The functions that operate on integers, such as abs, labs, div, and ldiv, are instead defined in the header ( header in C++). Any functions that operate on angles use radians as the unit of angle. Floating-point environment C99 adds several functions and types for fine-grained control of floating-point environment. Implementations are provided by open-source projects that are not part of the standard library. Type-generic functions The header defines a type-generic macro for each mathematical function defined in and . This adds a limited support for function overloading of the mathematical functions: the same function name can be used with different types of parameters; the actual function will be selected at compile time according to the types of the parameters. Each type-generic macro that corresponds to a function that is defined for both real and complex numbers encapsulates a total of 6 different functions: float, double and long double, and their complex variants. The type-generic macros that correspond to a function that is defined for only real numbers encapsulates a total of 3 different functions: float, double and long double variants of the function. The C++ language includes native support for function overloading and thus does not provide the header even as a compatibility feature. Random-number generation The header ( in C++) defines several functions that can be used for statistically random number generation. The arc4random family of random number functions are not defined in POSIX standard, but is found in some common libc implementations. It used to refer to the keystream generator of a leaked version of RC4 cipher (hence "alleged RC4"), but different algorithms, usually from other ciphers like ChaCha20, have been implemented since using the same name. The quality of randomness from rand are usually too weak to be even considered statistically random, and it requires explicit seeding. It is usually advised to use arc4random instead of rand when possible. Some C libraries implement rand using arc4random_uniform internally. Special functions Beginning in C++17, C++ introduces special functions into the header. == Implementations ==

Under POSIX systems like Linux and BSD, the mathematical functions (as declared in ) are bundled separately in the mathematical library . Therefore, if any of those functions are used, the linker must be given the directive -lm. There are various libm implementations, including: • GNU libc's libm • AMD's libm, github, used almost as is by Windows • Intel C++ Compiler libm • Red Hat's libm (Newlib) • Sun's FDLIBM, which was used as the basis for FreeBSD's msun and OpenBSD's libm, both of which in turn were the basis of Julia's OpenLibm • musl's libm, based on the BSD libms and other projects like Arm • LLVM's libm, which is correctly rounded (i.e. errors from the mathematically correct result are lower than 0.5 unit in the last place) • Arénaire project's CRlibm (correctly rounded libm), and its successor MetaLibm, which uses Remez algorithm to automatically generate approximations that are formally proven. • Rutger's RLIBM, which provides correctly rounded functions in single precision. Implementations not necessarily under a name of include: • Arm's • is a version of C/C++ math functions written for C++ (compile-time calculation) • CORE-MATH, correctly rounded for single and double precision. • SIMD (vectorized) math libraries include SLEEF, Yeppp! , and Agner Fog's VCL, plus a few closed-source ones like SVML and DirectXMath. == See also ==