std::log10, std::log10f, std::log10l

 

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Defined in header <cmath>
	(1)
float       log10 (float num ); double      log10 (double num ); longdouble log10 (longdouble num );			(until C++23)
/*floating-point-type*/             log10 (/*floating-point-type*/ num );			(since C++23) (constexpr since C++26)
float       log10f(float num );		(2)	(since C++11) (constexpr since C++26)
longdouble log10l(longdouble num );		(3)	(since C++11) (constexpr since C++26)
SIMD overload(since C++26)
Defined in header <simd>
template</*math-floating-point*/ V > constexpr/*deduced-simd-t*/<V>             log10 (const V& v_num );		(S)	(since C++26)
Additional overloads(since C++11)
Defined in header <cmath>
template<class Integer > double      log10 ( Integer num );		(A)	(constexpr since C++26)

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.)

(since C++26)

A) Additional overloads are provided for all integer types, which are treated as double.

(since C++11)

Parameters

num

-

floating-point or integer value

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.

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.

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)).

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 valuesstd::cout<<"log10(1) = "<< std::log10(1)<<'\n'<<"log10(+Inf) = "<< std::log10(INFINITY)<<'\n';   // error handlingerrno=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

See also

loglogflogl (C++11)(C++11)	computes natural (base e) logarithm (\({\small\ln{x}}\)ln(x)) (function)
log2log2flog2l (C++11)(C++11)(C++11)	base 2 logarithm of the given number (\({\small\log_{2}{x}}\)log2(x)) (function)
log1plog1pflog1pl (C++11)(C++11)(C++11)	natural logarithm (to base e) of 1 plus the given number (\({\small\ln{(1+x)}}\)ln(1+x)) (function)
log10(std::complex)	complex common logarithm with the branch cuts along the negative real axis (function template)
log10(std::valarray)	applies the function std::log10 to each element of valarray (function template)
C documentation for log10