NAME¶

std::log10(std::valarray) - std::log10(std::valarray)

Synopsis¶

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:

* All const member functions of std::valarray are provided.
* std::valarray, std::slice_array, std::gslice_array, std::mask_array and
std::indirect_array can be constructed from the replacement type.
* All functions accepting an argument of type const std::valarray&
except begin() and end()
(since C++11) should also accept the replacement type.
* All functions accepting two arguments of type const std::valarray&
should accept every combination of const std::valarray& and the
replacement type.
* The return type does not add more than two levels of template nesting
over the most deeply-nested argument type.

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¶

// Run this code

#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¶

log(std::valarray) applies the function std::log to each element of valarray
(function template)
log10
log10f computes common (base 10) logarithm (\({\small \log_{10}{x}
log10l }\)log[10](x))
(C++11) (function)
(C++11)
complex common logarithm with the branch cuts along the negative
log10(std::complex) real axis
(function template)