namespace std {
template<class T> class valarray {
public:
using value_type = T;
// [valarray.cons], construct/destroy
valarray();
explicit valarray(size_t);
valarray(const T&, size_t);
valarray(const T*, size_t);
valarray(const valarray&);
valarray(valarray&&) noexcept;
valarray(const slice_array<T>&);
valarray(const gslice_array<T>&);
valarray(const mask_array<T>&);
valarray(const indirect_array<T>&);
valarray(initializer_list<T>);
~valarray();
// [valarray.assign], assignment
valarray& operator=(const valarray&);
valarray& operator=(valarray&&) noexcept;
valarray& operator=(initializer_list<T>);
valarray& operator=(const T&);
valarray& operator=(const slice_array<T>&);
valarray& operator=(const gslice_array<T>&);
valarray& operator=(const mask_array<T>&);
valarray& operator=(const indirect_array<T>&);
// [valarray.access], element access
const T& operator[](size_t) const;
T& operator[](size_t);
// [valarray.sub], subset operations
valarray operator[](slice) const;
slice_array<T> operator[](slice);
valarray operator[](const gslice&) const;
gslice_array<T> operator[](const gslice&);
valarray operator[](const valarray<bool>&) const;
mask_array<T> operator[](const valarray<bool>&);
valarray operator[](const valarray<size_t>&) const;
indirect_array<T> operator[](const valarray<size_t>&);
// [valarray.unary], unary operators
valarray operator+() const;
valarray operator-() const;
valarray operator~() const;
valarray<bool> operator!() const;
// [valarray.cassign], compound assignment
valarray& operator*= (const T&);
valarray& operator/= (const T&);
valarray& operator%= (const T&);
valarray& operator+= (const T&);
valarray& operator-= (const T&);
valarray& operator^= (const T&);
valarray& operator&= (const T&);
valarray& operator|= (const T&);
valarray& operator<<=(const T&);
valarray& operator>>=(const T&);
valarray& operator*= (const valarray&);
valarray& operator/= (const valarray&);
valarray& operator%= (const valarray&);
valarray& operator+= (const valarray&);
valarray& operator-= (const valarray&);
valarray& operator^= (const valarray&);
valarray& operator|= (const valarray&);
valarray& operator&= (const valarray&);
valarray& operator<<=(const valarray&);
valarray& operator>>=(const valarray&);
// [valarray.members], member functions
void swap(valarray&) noexcept;
size_t size() const;
T sum() const;
T min() const;
T max() const;
valarray shift (int) const;
valarray cshift(int) const;
valarray apply(T func(T)) const;
valarray apply(T func(const T&)) const;
void resize(size_t sz, T c = T());
};
}
The class template valarray<T> is a one-dimensional smart array, with elements numbered sequentially from zero. It is a representation of the mathematical concept of an ordered set of values. The illusion of higher dimensionality may be produced by the familiar idiom of computed indices, together with the powerful subsetting capabilities provided by the generalized subscript operators.277
An implementation is permitted to qualify any of the functions declared in <valarray> as inline.
The intent is to specify an array template that has the minimum functionality necessary to address aliasing ambiguities and the proliferation of temporaries. Thus, the valarray template is neither a matrix class nor a field class. However, it is a very useful building block for designing such classes.
The array created by this constructor has a length equal to the value of the argument. The elements of the array are value-initialized ([dcl.init]).
The array created by this constructor has a length equal to the second argument. The elements of the array are initialized with the value of the first argument.
The array created by this constructor has a length equal to the second argument n. The values of the elements of the array are initialized with the first n values pointed to by the first argument.280 If the value of the second argument is greater than the number of values pointed to by the first argument, the behavior is undefined.
The array created by this constructor has the same length as the argument array. The elements are initialized with the values of the corresponding elements of the argument array.281
valarray(valarray&& v) noexcept;
The array created by this constructor has the same length as the argument array. The elements are initialized with the values of the corresponding elements of the argument array.
Complexity: Constant.
valarray(initializer_list<T> il);
Effects: Same as valarray(il.begin(), il.size()).
valarray(const slice_array<T>&);
valarray(const gslice_array<T>&);
valarray(const mask_array<T>&);
valarray(const indirect_array<T>&);
These conversion constructors convert one of the four reference templates to a valarray.
The destructor is applied to every element of *this; an implementation may return all allocated memory.
For convenience, such objects are referred to as “arrays” throughout the remainder of [numarray].
This default constructor is essential, since arrays of valarray may be useful. After initialization, the length of an empty array can be increased with the resize member function.
This constructor is the preferred method for converting a C array to a valarray object.
This copy constructor creates a distinct array rather than an alias. Implementations in which arrays share storage are permitted, but they shall implement a copy-on-reference mechanism to ensure that arrays are conceptually distinct.
valarray& operator=(const valarray& v);
Each element of the *this array is assigned the value of the corresponding element of the argument array. If the length of v is not equal to the length of *this , resizes *this to make the two arrays the same length, as if by calling resize(v.size()), before performing the assignment.
Postconditions: size() == v.size().
valarray& operator=(valarray&& v) noexcept;
Effects: *this obtains the value of v. The value of v after the assignment is not specified.
Complexity: Linear.
valarray& operator=(initializer_list<T> il);
Effects: As if by: *this = valarray(il);
Returns: *this.
valarray& operator=(const T&);
The scalar assignment operator causes each element of the *this array to be assigned the value of the argument.
valarray& operator=(const slice_array<T>&);
valarray& operator=(const gslice_array<T>&);
valarray& operator=(const mask_array<T>&);
valarray& operator=(const indirect_array<T>&);
Requires: The length of the array to which the argument refers equals size().
These operators allow the results of a generalized subscripting operation to be assigned directly to a valarray.
If the value of an element in the left-hand side of a valarray assignment operator depends on the value of another element in that left-hand side, the behavior is undefined.
const T& operator[](size_t) const;
T& operator[](size_t);
The subscript operator returns a reference to the corresponding element of the array.
Thus, the expression (a[i] = q, a[i]) == q evaluates as true for any non-constant valarray<T> a, any T q, and for any size_t i such that the value of i is less than the length of a.
The expression &a[i+j] == &a[i] + j evaluates as true for all size_t i and size_t j such that i+j is less than the length of the array a.
Likewise, the expression &a[i] != &b[j] evaluates as true for any two arrays a and b and for any size_t i and size_t j such that i is less than the length of a and j is less than the length of b. This property indicates an absence of aliasing and may be used to advantage by optimizing compilers.282
The reference returned by the subscript operator for an array shall be valid until the member function resize(size_t, T) ([valarray.members]) is called for that array or until the lifetime of that array ends, whichever happens first.
Compilers may take advantage of inlining, constant propagation, loop fusion, tracking of pointers obtained from operator new, and other techniques to generate efficient valarrays.
The member operator[] is overloaded to provide several ways to select sequences of elements from among those controlled by *this. Each of these operations returns a subset of the array. The const-qualified versions return this subset as a new valarray object. The non-const versions return a class template object which has reference semantics to the original array, working in conjunction with various overloads of operator= and other assigning operators to allow selective replacement (slicing) of the controlled sequence. In each case the selected element(s) must exist.
Returns: An object of class valarray<T> containing those elements of the controlled sequence designated by slicearr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
// v0[slice(2, 5, 3)] returns valarray<char>("cfilo", 5)
— end example ]
slice_array<T> operator[](slice slicearr);
Returns: An object that holds references to elements of the controlled sequence selected by slicearr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDE", 5);
v0[slice(2, 5, 3)] = v1;
// v0 == valarray<char>("abAdeBghCjkDmnEp", 16);
— end example ]
valarray operator[](const gslice& gslicearr) const;
Returns: An object of class valarray<T> containing those elements of the controlled sequence designated by gslicearr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const size_t lv[] = { 2, 3 };
const size_t dv[] = { 7, 2 };
const valarray<size_t> len(lv, 2), str(dv, 2);
// v0[gslice(3, len, str)] returns
// valarray<char>("dfhkmo", 6)
— end example ]
gslice_array<T> operator[](const gslice& gslicearr);
Returns: An object that holds references to elements of the controlled sequence selected by gslicearr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDEF", 6);
const size_t lv[] = { 2, 3 };
const size_t dv[] = { 7, 2 };
const valarray<size_t> len(lv, 2), str(dv, 2);
v0[gslice(3, len, str)] = v1;
// v0 == valarray<char>("abcAeBgCijDlEnFp", 16)
— end example ]
valarray operator[](const valarray<bool>& boolarr) const;
Returns: An object of class valarray<T> containing those elements of the controlled sequence designated by boolarr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const bool vb[] = { false, false, true, true, false, true };
// v0[valarray<bool>(vb, 6)] returns
// valarray<char>("cdf", 3)
— end example ]
mask_array<T> operator[](const valarray<bool>& boolarr);
Returns: An object that holds references to elements of the controlled sequence selected by boolarr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABC", 3);
const bool vb[] = { false, false, true, true, false, true };
v0[valarray<bool>(vb, 6)] = v1;
// v0 == valarray<char>("abABeCghijklmnop", 16)
— end example ]
valarray operator[](const valarray<size_t>& indarr) const;
Returns: An object of class valarray<T> containing those elements of the controlled sequence designated by indarr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const size_t vi[] = { 7, 5, 2, 3, 8 };
// v0[valarray<size_t>(vi, 5)] returns
// valarray<char>("hfcdi", 5)
— end example ]
indirect_array<T> operator[](const valarray<size_t>& indarr);
Returns: An object that holds references to elements of the controlled sequence selected by indarr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDE", 5);
const size_t vi[] = { 7, 5, 2, 3, 8 };
v0[valarray<size_t>(vi, 5)] = v1;
// v0 == valarray<char>("abCDeBgAEjklmnop", 16)
— end example ]
valarray operator+() const;
valarray operator-() const;
valarray operator~() const;
valarray<bool> operator!() const;
Each of these operators may only be instantiated for a type T to which the indicated operator can be applied and for which the indicated operator returns a value which is of type T (bool for operator!) or which may be unambiguously implicitly converted to type T (bool for operator!).
Each of these operators returns an array whose length is equal to the length of the array. Each element of the returned array is initialized with the result of applying the indicated operator to the corresponding element of the array.
valarray& operator*= (const valarray&);
valarray& operator/= (const valarray&);
valarray& operator%= (const valarray&);
valarray& operator+= (const valarray&);
valarray& operator-= (const valarray&);
valarray& operator^= (const valarray&);
valarray& operator&= (const valarray&);
valarray& operator|= (const valarray&);
valarray& operator<<=(const valarray&);
valarray& operator>>=(const valarray&);
Each of these operators may only be instantiated for a type T to which the indicated operator can be applied. Each of these operators performs the indicated operation on each of its elements and the corresponding element of the argument array.
The array is then returned by reference.
If the value of an element in the left-hand side of a valarray compound assignment operator depends on the value of another element in that left hand side, the behavior is undefined.
valarray& operator*= (const T&);
valarray& operator/= (const T&);
valarray& operator%= (const T&);
valarray& operator+= (const T&);
valarray& operator-= (const T&);
valarray& operator^= (const T&);
valarray& operator&= (const T&);
valarray& operator|= (const T&);
valarray& operator<<=(const T&);
valarray& operator>>=(const T&);
Each of these operators may only be instantiated for a type T to which the indicated operator can be applied.
Each of these operators applies the indicated operation to each element of the array and the non-array argument.
The array is then returned by reference.
The appearance of an array on the left-hand side of a compound assignment does not invalidate references or pointers to the elements of the array.
void swap(valarray& v) noexcept;
Effects: *this obtains the value of v. v obtains the value of *this.
Complexity: Constant.
Returns: The number of elements in the array.
Complexity: Constant time.
This function may only be instantiated for a type T to which operator+= can be applied. This function returns the sum of all the elements of the array.
This function returns the minimum value contained in *this. The value returned for an array of length 0 is undefined. For an array of length 1, the value of element 0 is returned. For all other array lengths, the determination is made using operator<.
This function returns the maximum value contained in *this. The value returned for an array of length 0 is undefined. For an array of length 1, the value of element 0 is returned. For all other array lengths, the determination is made using operator<.
This function returns an object of class valarray<T> of length size(), each of whose elements I is (*this)[I + n] if I + n is non-negative and less than size(), otherwise T(). Thus if element zero is taken as the leftmost element, a positive value of n shifts the elements left n places, with zero fill.
[ Example: If the argument has the value -2, the first two elements of the result will be value-initialized ([dcl.init]); the third element of the result will be assigned the value of the first element of the argument; etc. — end example ]
This function returns an object of class valarray<T> of length size() that is a circular shift of *this. If element zero is taken as the leftmost element, a non-negative value of n shifts the elements circularly left n places and a negative value of n shifts the elements circularly right -n places.
valarray apply(T func(T)) const;
valarray apply(T func(const T&)) const;
These functions return an array whose length is equal to the array. Each element of the returned array is assigned the value returned by applying the argument function to the corresponding element of the array.
void resize(size_t sz, T c = T());
This member function changes the length of the *this array to sz and then assigns to each element the value of the second argument. Resizing invalidates all pointers and references to elements in the array.