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std::log10(std::valarray)

From cppreference.com
< 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.

Contents

[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;
}

[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);
}

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

[edit] See also

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