std::valarray::operator[]
From cppreference.com
(1) | ||
T operator[]( std::size_t pos ) const;
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(until C++11) | |
const T& operator[]( std::size_t pos ) const;
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(since C++11) | |
T& operator[]( std::size_t pos );
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(2) | |
std::valarray<T> operator[]( std::slice slicearr ) const;
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(3) | |
std::slice_array<T> operator[]( std::slice slicearr );
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(4) | |
std::valarray<T> operator[]( const std::gslice& gslicearr ) const;
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(5) | |
std::gslice_array<T> operator[]( const std::gslice& gslicearr );
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(6) | |
std::valarray<T> operator[]( const valarray<bool>& boolarr ) const;
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(7) | |
std::mask_array<T> operator[]( const valarray<bool>& boolarr );
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(8) | |
std::valarray<T> operator[]( const valarray<std::size_t>& indarr ) const;
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(9) | |
std::indirect_array<T> operator[]( const valarray<std::size_t>& indarr );
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(10) | |
Retrieve single elements or portions of the array.
The const overloads that return element sequences create a new std::valarray object. The non-const overloads return classes holding references to the array elements.
Contents |
[edit] Parameters
This section is incomplete Reason: Explain the parameters |
[edit] Return value
1,2) A reference to the corresponding element
3,5,7,9) A std::valarray object containing copies of the selected items
4,6,8,10) The corresponding data structure containing references to the selected items
[edit] Exceptions
(none)
[edit] Precondition
The selected elements must exist.
[edit] Notes
- For proper values of
i
andj
, the following properties are true:
1) (a[i] = q, a[i]) == q
- For a non-const
a
.
2) &a[i+j] == &a[i] + j
- This means that valarray elements are adjacent in memory.
3) &a[i] != &b[j]
- This holds for every objects
a
andb
that are not aliases of one another. - This means that there are no aliases in the elements and this property can be used to perform some kinds of optimization.
- References become invalid on resize or when the array is destructed.
For overloads (3,5,7,9), 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++14) 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.
[edit] Example
This section is incomplete Reason: no example |