std::log10, std::log10f, std::log10l
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Defined in header
<cmath>
(1)
float log10 ( float num );
(until C++23)
double log10 ( double num );
/*floating-point-type*/
log10 ( /*floating-point-type*/ num );
(since C++23) log10 ( /*floating-point-type*/ num );
(constexpr since C++26)
float log10f( float num );
(2)
(since C++11) (constexpr since C++26)
long double log10l( long double num );
(3)
(since C++11) (constexpr since C++26)
SIMD overload (since C++26)
Defined in header
<simd>
template< /*math-floating-point*/ V >
(S)
(since C++26)
constexpr /*deduced-simd-t*/<V>
Additional overloads (since C++11)
Defined in header
<cmath>
template< class Integer >
double log10 ( Integer num );
(A)
(constexpr since C++26)
double log10 ( Integer num );
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)S) The SIMD overload performs an element-wise
std::log10 on v_num.- (See math-floating-point and deduced-simd-t for their definitions.)
A) Additional overloads are provided for all integer types, which are treated as double.
(since C++11)[edit] Parameters
num
-
floating-point or integer value
[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
Run this code
#include <cerrno> #include <cfenv> #include <cmath> #include <cstring> #include <iostream> // #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
(C++11)(C++11)(C++11)
(function) [edit]
(C++11)(C++11)(C++11)
(function) [edit]
complex common logarithm with the branch cuts along the negative real axis
(function template) [edit]
(function template) [edit]
C documentation for log10