std::log(std::valarray) - cppreference.com (original) (raw)
| | | | | --------------------------------------------------------------- | | | | template< class T >valarray<T> log( const valarray<T>& va ); | | |
For each element in va computes natural logarithm of the value of the element.
Contents
[edit] Parameters
| va | - | value array to apply the operation to |
|---|
[edit] Return value
Value array containing natural logarithms of the values in va.
[edit] Notes
Unqualified function (log) is used to perform the computation. If such function is not available, std::log 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 log(const valarray& va) { valarray other = va; for (T& i : other) i = log(i); return other; // proxy object may be returned }
[edit] Example
Output:
n : 0.000000 1.000000 2.000000 3.000000 eⁿ : 1.000000 2.718282 7.389056 20.085537 log(eⁿ) : 0.000000 1.000000 2.000000 3.000000