std::log10, std::log10f, std::log10l - cppreference.com (original) (raw)

1-3) Computes the common (base-10) logarithm of num. The library provides overloads of std::log10 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, the common (base-10) logarithm of num (log10(num) or lg(num)) is returned.

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

If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.

[edit] Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if num is less than zero.

Pole error may occur if num is zero.

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

• If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
• If the argument is 1, +0 is returned.
• If the argument is negative, NaN is returned and FE_INVALID is raised.
• If the argument is +∞, +∞ is returned.
• If the argument is NaN, NaN is returned.

[edit] Notes

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::log10(num) has the same effect as std::log10(static_cast<double>(num)).

[edit] Example

#include #include #include #include #include // #pragma STDC FENV_ACCESS ON   int main() { std::cout << "log10(1000) = " << std::log10(1000) << '\n' << "log10(0.001) = " << std::log10(0.001) << '\n' << "base-5 logarithm of 125 = " << std::log10(125) / std::log10(5) << '\n';   // special values std::cout << "log10(1) = " << std::log10(1) << '\n' << "log10(+Inf) = " << std::log10(INFINITY) << '\n';   // error handling errno = 0; std::feclearexcept(FE_ALL_EXCEPT);   std::cout << "log10(0) = " << std::log10(0) << '\n';   if (errno == ERANGE) std::cout << " errno == ERANGE: " << std::strerror(errno) << '\n'; if (std::fetestexcept(FE_DIVBYZERO)) std::cout << " FE_DIVBYZERO raised\n"; }

Possible output:

log10(1000) = 3 log10(0.001) = -3 base-5 logarithm of 125 = 3 log10(1) = 0 log10(+Inf) = inf log10(0) = -inf errno == ERANGE: Numerical result out of range FE_DIVBYZERO raised

[edit] See also