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

Since C++26

Header: <cmath>

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)

# Declarations

float log10 ( float num );
double log10 ( double num );
long double log10 ( long double num );

(until C++23)

/*floating-point-type*/
log10 ( /*floating-point-type*/ num );

(since C++23) (constexpr since C++26)

float log10f( float num );

(since C++11) (constexpr since C++26)

long double log10l( long double num );

(since C++11) (constexpr since C++26)

SIMD overload (since C++26)

template< /*math-floating-point*/ V >
constexpr /*deduced-simd-t*/<V>
log10 ( const V& v_num );

(since C++26)

Additional overloads (since C++11)

template< class Integer >
double log10 ( Integer num );

(constexpr since C++26)

# Parameters

# Return value

If no errors occur, the common (base-10) logarithm of num (log10(num) or lg(num)) 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(num)).

# 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";
}

# See also