std::log10, std::log10f, std::log10l
Defined in header <cmath>
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(1) | ||
float log10 ( float num ); double log10 ( double num ); |
(until C++23) | |
/* floating-point-type */ log10 ( /* floating-point-type */ num ); |
(since C++23) (constexpr since C++26) |
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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) |
Additional overloads (since C++11) |
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Defined in header <cmath>
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template< class Integer > double log10 ( Integer num ); |
(A) | (constexpr since C++26) |
std::log10
for all cv-unqualified floating-point types as the type of the parameter.(since C++23)
A) Additional overloads are provided for all integer types, which are treated as double.
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(since C++11) |
Contents |
[edit] Parameters
num | - | floating-point or integer value |
[edit] Return value
If no errors occur, the common (base-10) logarithm of num (log
10(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 <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) |
computes natural (base e) logarithm (ln(x)) (function) |
(C++11)(C++11)(C++11) |
base 2 logarithm of the given number (log2(x)) (function) |
(C++11)(C++11)(C++11) |
natural logarithm (to base e) of 1 plus the given number (ln(1+x)) (function) |
complex common logarithm with the branch cuts along the negative real axis (function template) | |
applies the function std::log10 to each element of valarray (function template) | |
C documentation for log10
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