std::log10(std::valarray) - cppreference.com (original) (raw)
| | | | | ----------------------------------------------------------------- | | | | 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:
- 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.
- For every function taking a const std::valarray<T>& except begin() and end()(since C++11), identical functions taking the replacement types shall be added;
- For every function taking two const std::valarray<T>& arguments, identical functions taking every combination of const std::valarray<T>& and replacement types shall be added.
- The return type does not add more than two levels of template nesting over the most deeply-nested argument type.
[edit] Possible implementation
template valarray log10(const valarray& va) { valarray other = va; for (T& i : other) i = log10(i); return other; // proxy object may be returned }
[edit] Example
#include #include #include #include void show(char const* title, const std::valarray& va) { std::cout << title << " : " << std::right; for (float x : va) std::cout << std::setw(6) << x; std::cout << '\n'; } int main() { const std::valarray n{-2.f, -1.f, 0.f, 1.f, 2.f, 3.f, INFINITY}; const std::valarray pow10{std::pow(10.f, n)}; const std::valarray 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