sqrtfL

sqrtfL is a non-standard function name that appears in some codebases to denote the square root operation for long double precision. It is not part of the ISO C standard math library, and its exact signature or behavior can vary between projects. In standard C and C++, square root operations are provided by sqrtf for float, sqrt for double, and sqrtl for long double, or by a type-generic overload in C++. Therefore, sqrtfL is typically an alias or wrapper around the long double variant rather than a universally defined function.

In practice, if a library defines sqrtfL, it is usually intended to yield the principal square root of a long double input, with a signature such as long double sqrtfL(long double x). Implementations may simply forward to sqrtl(x) or provide a custom long double routine. As with other square root functions, domain errors occur for negative inputs in real-number contexts, and the result for negative arguments is typically NaN.

Usage and portability considerations are important. Since sqrtfL is not standardized, code relying on it may be less portable across compilers and platforms. If cross-platform compatibility is a concern, developers often use the standard sqrtl for long double or employ a type-generic approach (such as C11 _Generic or C++ overloading) to select the appropriate sqrt variant automatically. When documenting code that uses sqrtfL, it is helpful to specify the exact implementation or provide a clear alias to sqrtl to avoid ambiguity.

See also: sqrtf, sqrt, sqrtl, type-generic math, numeric precision.