std::sqrt, std::sqrtf, std::sqrtl - cppreference.com (original) (raw)

1-3) Computes the square root of num. The library provides overloads of std::sqrt for all cv-unqualified floating-point types as the type of the parameter.(since C++23)

[edit] Parameters

[edit] Return value

If no errors occur, square root of num (\({\small \sqrt{num} }\)√num), is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a range error occurs due to underflow, the correct result (after rounding) is returned.

[edit] Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if num is less than zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is less than -0, FE_INVALID is raised and NaN is returned.
• If the argument is +∞ or ±0, it is returned, unmodified.
• If the argument is NaN, NaN is returned.

[edit] Notes

std::sqrt is required by the IEEE standard to be correctly rounded from the infinitely precise result. In particular, the exact result is produced if it can be represented in the floating-point type. The only other operations which require this are the arithmetic operators and the function std::fma. Other functions, including std::pow, are not so constrained.

The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::sqrt(num) has the same effect as std::sqrt(static_cast<double>(num)).

[edit] Example

#include #include #include #include #include // #pragma STDC FENV_ACCESS ON   int main() { // normal use std::cout << "sqrt(100) = " << std::sqrt(100) << '\n' << "sqrt(2) = " << std::sqrt(2) << '\n' << "golden ratio = " << (1 + std::sqrt(5)) / 2 << '\n';   // special values std::cout << "sqrt(-0) = " << std::sqrt(-0.0) << '\n';   // error handling errno = 0; std::feclearexcept(FE_ALL_EXCEPT);   std::cout << "sqrt(-1.0) = " << std::sqrt(-1) << '\n'; if (errno == EDOM) std::cout << " errno = EDOM " << std::strerror(errno) << '\n'; if (std::fetestexcept(FE_INVALID)) std::cout << " FE_INVALID raised\n"; }

Possible output:

sqrt(100) = 10 sqrt(2) = 1.41421 golden ratio = 1.61803 sqrt(-0) = -0 sqrt(-1.0) = -nan errno = EDOM Numerical argument out of domain FE_INVALID raised

[edit] See also