< cpp‎ | numeric‎ | 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.


[edit] Parameters

va - value array to apply the operation to

[edit] Return value

Value array containing common logarithms of the values in va.

[edit] 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:

[edit] 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

[edit] 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);


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

[edit] See also

applies the function std::log to each element of valarray
(function template) [edit]
computes common (base 10) logarithm (log10(x))
(function) [edit]
complex common logarithm with the branch cuts along the negative real axis
(function template) [edit]