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std::log10(std::valarray)

Defined in header <valarray>
template< class T >
valarray<T> log10( const valarray<T>& va );

For each element in va computes common (base 10) logarithm of the value of the element.

Parameters

va - value array to apply the operation to

Return value

Value array containing common logarithms of the values in va.

Notes

Unqualified function (log10) is used to perform the computation. If such function is not available, std::log10 is used due to argument-dependent lookup.

The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:

Possible implementation

template< class T >
valarray<T> log10( const valarray<T>& va )
{
    valarray<T> other = va;
    for (T &i : other)
        i = log10(i);
 
    return other; // proxy object may be returned
}

Example

#include <cmath>
#include <iomanip>
#include <iostream>
#include <valarray>
 
void show(char const* title, const std::valarray<float>& va)
{
    std::cout << title << " : " << std::right;
    for (float x : va) {
        std::cout << std::setw(6) << x;
    }
    std::cout << '\n';
}
 
int main()
{
    const std::valarray<float> n { -2.f, -1.f, 0.f, 1.f, 2.f, 3.f, INFINITY };
    const std::valarray<float> pow10 { std::pow(10.f, n) };
    const std::valarray<float> log10_pow10 { std::log10(pow10) };
 
    show("n      ", n);
    show("10ⁿ    ", pow10);
    show("lg(10ⁿ)", log10_pow10);
}

Output:

n       :     -2    -1     0     1     2     3   inf
10ⁿ     :   0.01   0.1     1    10   100  1000   inf
lg(10ⁿ) :     -2    -1     0     1     2     3   inf

See also

applies the function std::log to each element of valarray
(function template)
(C++11)(C++11)
computes common (base 10) logarithm (\({\small \log_{10}{x} }\)log10(x))
(function)
complex common logarithm with the branch cuts along the negative real axis
(function template)

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