`valarray` class

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06/21/2022

The class template valarray<Type> describes an object that controls a sequence of elements of type Type that are stored as an array, designed for high-speed mathematical operations, and optimized for computational performance.

Remarks

The class is a representation of the mathematical concept of an ordered set of values. Its elements are numbered sequentially from zero. The class is described as a near container because it supports some, but not all, of the capabilities that first-class sequence containers, such as vector, support. It differs from class template vector in two important ways:

It defines many arithmetic operations between corresponding elements of valarray<Type> objects of the same type and length, such as varr_x* = cos(varr_y) + sin(varr_z).
It defines various interesting ways to subscript a valarray<Type> object, by overloading operator[].

An object of class Type:

Has a public default constructor, destructor, copy constructor, and assignment operator, with conventional behavior.
Defines the arithmetic operators and math functions, as needed, that are defined for the floating-point types, with conventional behavior.

In particular, no subtle differences may exist between copy construction and default construction followed by assignment. None of the operations on objects of class Type may throw exceptions.

Members

Constructors

Name	Description
`valarray`	Constructs a `valarray` of a specific size or with elements of a specific value or as a copy of another `valarray` or subset of another `valarray`.

Typedefs

Name	Description
`value_type`	A type that represents the type of element stored in a `valarray`.

Functions

Name	Description
`apply`	Applies a specified function to each element of a `valarray`.
`cshift`	Cyclically shifts all the elements in a `valarray` by a specified number of positions.
`free`	Frees the memory used by the `valarray`.
`max`	Finds the largest element in a `valarray`.
`min`	Finds the smallest element in a `valarray`.
`resize`	Changes the number of elements in a `valarray` to a specified number, adding or removing elements as required.
`shift`	Shifts all the elements in a `valarray` by a specified number of positions.
`size`	Finds the number of elements in a `valarray`.
`sum`	Determines the sum of all the elements in a `valarray` of nonzero length.
`swap`

Operators

Name	Description
`operator!`	A unary operator that obtains the logical NOT (`!`) values of each element in a `valarray`.
`operator%=`	Obtains the remainder of dividing the elements of an array element-wise either by a specified `valarray` or by a value of the element type.
`operator&=`	Obtains the bitwise AND (`&`) of elements in an array either with the corresponding elements in a specified `valarray` or with a value of the element type.
`operator>>=`	Right-shifts the bits for each element of a `valarray` operand a specified number of positions or by an element-wise amount specified by a second `valarray`.
`operator<<=`	Left-shifts the bits for each element of a `valarray` operand a specified number of positions or by an element-wise amount specified by a second `valarray`.
`operator*=`	Multiplies the elements of a specified `valarray` or a value of the element type, element-wise, to an operand `valarray`.
`operator+`	A unary operator that applies a plus to each element in a `valarray`. On normal arithmetic types, this operator has no effect.
`operator+=`	Adds the elements of a specified `valarray` or a value of the element type, element-wise, to an operand `valarray`.
`operator-`	A unary operator that applies an arithmetic negation to each element in a `valarray`.
`operator-=`	Subtracts the elements of a specified `valarray` or a value of the element type, element-wise, from an operand `valarray`.
`operator/=`	Divides an operand `valarray` element-wise by the elements of a specified `valarray` or a value of the element type.
`operator=`	Assigns elements to a `valarray` whose values are specified either directly or as part of some other `valarray` or by a `slice_array`, `gslice_array`, `mask_array`, or `indirect_array`.
`operator[]`	Returns a reference to an element or its value at specified index or a specified subset.
`operator^=`	Obtains the bitwise exclusive or (`^`) of a `valarray` with either a specified `valarray` or a value of the element type.
`operator\|=`	Obtains the bitwise OR (`\|`) of elements in an array either with the corresponding elements in a specified `valarray` or with a value of the element type.
`operator~`	A unary operator that obtains the bitwise complement (`~`) values of each element in a `valarray`.

`apply`

Applies a specified function to each element of a valarray.

valarray<Type> apply(Type function_object(Type)) const;

valarray<Type> apply(Type function_object(const Type&)) const;

Parameters

function_object(Type)
The function object to be applied to each element of the operand valarray.

function_object(const Type&)
The function object for const elements to be applied to each element of the operand valarray.

Return value

A valarray whose elements have had function_object applied element-wise to the elements of the operand valarray.

Remarks

The member function returns an object of class valarray<Type>, of length size, each of whose elements elem is the result of function_object((*this)[elem]).

Example

// valarray_apply.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

using namespace std;

int __cdecl MyApplyFunc( int n )
{
   return n*2;
}

int main( int argc, char* argv[] )
{
   valarray<int> vaR(10), vaApplied(10);
   int i;

   for ( i = 0; i < 10; i += 3 )
      vaR[i] = i;

   for ( i = 1; i < 10; i += 3 )
      vaR[i] = 0;

   for ( i = 2; i < 10; i += 3 )
      vaR[i] = -i;

   cout << "The initial Right valarray is: (";
   for   ( i=0; i < 10; ++i )
      cout << " " << vaR[i];
   cout << " )" << endl;

   vaApplied = vaR.apply( MyApplyFunc );

   cout << "The element-by-element result of "
       << "applying MyApplyFunc to vaR is the\nvalarray: ( ";
   for ( i = 0; i < 10; ++i )
      cout << " " << vaApplied[i];
   cout << " )" << endl;
}

The initial Right valarray is: ( 0 0 -2 3 0 -5 6 0 -8 9 )
The element-by-element result of applying MyApplyFunc to vaR is the
valarray: (  0 0 -4 6 0 -10 12 0 -16 18 )

`cshift`

Cyclically shifts all the elements in a valarray by a specified number of positions.

valarray<Type> cshift(int count) const;

Parameters

count
The number of places the elements are to be shifted forward.

Return value

A new valarray in which all the elements have been moved count positions cyclically toward the front of the valarray, or leftward compared to their positions in the operand valarray.

Remarks

A positive value of count shifts the elements cyclically left count places.

A negative value of count shifts the elements cyclically right count places.

Example

// valarray_cshift.cpp
// compile with: /EHsc

#include <valarray>
#include <iostream>

int main()
{
    using namespace std;
    int i;

    valarray<int> va1(10), va2(10);
    for (i = 0; i < 10; i+=1)
        va1[i] = i;
    for (i = 0; i < 10; i+=1)
        va2[i] = 10 - i;

    cout << "The operand valarray va1 is: (";
    for (i = 0; i < 10; i++)
        cout << " " << va1[i];
    cout << ")" << endl;

    // A positive parameter shifts elements right
    va1 = va1.cshift(4);
    cout << "The cyclically shifted valarray va1 is:\nva1.cshift (4) = (";
    for (i = 0; i < 10; i++)
        cout << " " << va1[i];
    cout << ")" << endl;

    cout << "The operand valarray va2 is: (";
    for (i = 0; i < 10; i++)
        cout << " " << va2[i];
    cout << ")" << endl;

    // A negative parameter shifts elements left
    va2 = va2.cshift(-4);
    cout << "The cyclically shifted valarray va2 is:\nva2.shift (-4) = (";
    for (i = 0; i < 10; i++)
        cout << " " << va2[i];
    cout << ")" << endl;
}

The operand valarray va1 is: ( 0 1 2 3 4 5 6 7 8 9)
The cyclically shifted valarray va1 is:
va1.cshift (4) = ( 4 5 6 7 8 9 0 1 2 3)
The operand valarray va2 is: ( 10 9 8 7 6 5 4 3 2 1)
The cyclically shifted valarray va2 is:
va2.shift (-4) = ( 4 3 2 1 10 9 8 7 6 5)

`free`

Frees the memory used by the valarray.

void free();

Remarks

This nonstandard function is equivalent to assigning an empty valarray. For example:

valarray<T> v;
v = valarray<T>();

// equivalent to v.free()

`max`

Finds the largest element in a valarray.

Type max() const;

Return value

The maximum value of the elements in the operand valarray.

Remarks

The member function compares values by applying operator< or operator> between pairs of elements of class Type, for which operators must be provided for the element Type.

Example

// valarray_max.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i, MaxValue;

   valarray<int> vaR ( 10 );
   for ( i = 0 ; i < 10 ; i += 3 )
      vaR [ i ] =  i;
   for ( i = 1 ; i < 10 ; i += 3 )
      vaR [ i ] =  2*i - 1;
   for ( i = 2 ; i < 10 ; i += 3 )
      vaR [ i ] =  10 - i;

   cout << "The operand valarray is: ( ";
      for (i = 0 ; i < 10 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   MaxValue = vaR.max (  );
   cout << "The largest element in the valarray is: "
        << MaxValue  << "." << endl;
}

The operand valarray is: ( 0 1 8 3 7 5 6 13 2 9 ).
The largest element in the valarray is: 13.

`min`

Finds the smallest element in a valarray.

Type min() const;

Return value

The minimum value of the elements in the operand valarray.

Remarks

The member function compares values by applying operator< or operator> between pairs of elements of class Type, for which operators must be provided for the element Type.

Example

// valarray_min.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i, MinValue;

   valarray<int> vaR ( 10 );
   for ( i = 0 ; i < 10 ; i += 3 )
      vaR [ i ] =  -i;
   for ( i = 1 ; i < 10 ; i += 3 )
      vaR [ i ] =  2*i;
   for ( i = 2 ; i < 10 ; i += 3 )
      vaR [ i ] =  5 - i;

   cout << "The operand valarray is: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   MinValue = vaR.min ( );
   cout << "The smallest element in the valarray is: "
        << MinValue  << "." << endl;
}
/* Output:
The operand valarray is: ( 0 2 3 -3 8 0 -6 14 -3 -9 ).
The smallest element in the valarray is: -9.
*/

`operator!`

A unary operator that obtains the logical NOT (!) values of each element in a valarray.

valarray<bool> operator!() const;

Return value

The valarray of Boolean values that are the logical negation of the element values of the operand valarray.

Remarks

The logical operation NOT, denoted by !, logically negates the elements because it converts all zero values into true and all non-zero values into false. The returned valarray of Boolean values is of the same size as the operand valarray.

Example

// valarray_op_lognot.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 10 );
   valarray<bool> vaNOT ( 10 );
   for ( i = 0 ; i < 10 ; i += 2 )
      vaL [ i ] =  0;
   for ( i = 1 ; i < 10 ; i += 2 )
      vaL [ i ] =  i-1;

   cout << "The initial valarray is:  ( ";
      for (i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   vaNOT = !vaL;
   cout << "The element-by-element result of "
        << "the logical NOT operator! is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaNOT [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is:  ( 0 0 0 2 0 4 0 6 0 8 ).
The element-by-element result of the logical NOT operator! is the
valarray: ( 1 1 1 0 1 0 1 0 1 0 ).

`operator%=`

Obtains the remainder of dividing the elements of an array element-wise either by a specified valarray or by a value of the element type.

valarray<Type>& operator%=(const valarray<Type>& right);

valarray<Type>& operator%=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to divide, element-wise, the operand valarray.

Return value

A valarray whose elements are the remainder from the element-wise division of the operand valarray by right.

Example

// valarray_class_op_rem.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 6 ), vaR ( 6 );
   for ( i = 0 ; i < 6 ; i += 2 )
      vaL [ i ] =  53;
   for ( i = 1 ; i < 6 ; i += 2 )
      vaL [ i ] =  -67;
   for ( i = 0 ; i < 6 ; i++ )
      vaR [ i ] =  3*i+1;

   cout << "The initial valarray is: ( ";
      for ( i = 0 ; i < 6 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial  right valarray is: ( ";
      for ( i = 0 ; i < 6 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL %= vaR;
   cout << "The remainders from the element-by-element "
        << "division is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 6 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is: ( 53 -67 53 -67 53 -67 ).
The initial  right valarray is: ( 1 4 7 10 13 16 ).
The remainders from the element-by-element division is the
valarray: ( 0 -3 4 -7 1 -3 ).

`operator&=`

Obtains the bitwise AND (&) of elements in an array either with the corresponding elements in a specified valarray or with a value of the element type.

valarray<Type>& operator&=(const valarray<Type>& right);

valarray<Type>& operator&=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be combined, element-wise, by the bitwise AND (&) with the operand valarray.

Return value

A valarray whose elements are the bitwise AND (&) of the operand valarray by right

Remarks

A bitwise operation can only be used to manipulate bits in integral data types, such as char and int. It doesn't work on float, double, long double, void, bool, or other, more complex data types.

The bitwise AND (&) applies to the data type on the level of the individual bits. Given bits b1 and b2, b1 & b2 is 1 if both bits are 1; 0 if at least one bit is 0.

Example

// valarray_class_op_bitand.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 10 ), vaR ( 10 );
   for ( i = 0 ; i < 10 ; i += 2 )
      vaL [ i ] =  0;
   for ( i = 1 ; i < 10 ; i += 2 )
      vaL [ i ] =  i-1;
   for ( i = 0 ; i < 10 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial valarray is:  ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial Right valarray is: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL &= vaR;
   cout << "The element-by-element result of "
        << "the bitwise AND operator&= is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is:  ( 0 0 0 2 0 4 0 6 0 8 ).
The initial Right valarray is: ( 0 1 2 3 4 5 6 7 8 9 ).
The element-by-element result of the bitwise AND operator&= is the
valarray: ( 0 0 0 2 0 4 0 6 0 8 ).

`operator>>=`

Right-shifts the bits for each element of a valarray operand a specified number of positions or by an element-wise amount specified by a second valarray.

valarray<Type>& operator>>=(const valarray<Type>& right);

valarray<Type>& operator>>=(const Type& right);

Parameters

right
The value indicating the amount of right shift or a valarray whose elements indicate the element-wise amount of right shift.

Return value

A valarray whose elements have been shifted right the amount specified in right.

Remarks

Signed numbers have their signs preserved.

Example

// valarray_class_op_rs.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 8 ), vaR ( 8 );
   for ( i = 0 ; i < 8 ; i += 2 )
      vaL [ i ] =  64;
   for ( i = 1 ; i < 8 ; i += 2 )
      vaL [ i ] =  -64;
   for ( i = 0 ; i < 8 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial operand valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The  right valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL >>= vaR;
   cout << "The element-by-element result of "
        << "the right shift is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial operand valarray is: ( 64 -64 64 -64 64 -64 64 -64 ).
The  right valarray is: ( 0 1 2 3 4 5 6 7 ).
The element-by-element result of the right shift is the
valarray: ( 64 -32 16 -8 4 -2 1 -1 ).

`operator<<=`

Left-shifts the bits for each element of a valarray operand a specified number of positions or by an element-wise amount specified by a second valarray.

valarray<Type>& operator<<=(const valarray<Type>& right);

valarray<Type>& operator<<=(const Type& right);

Parameters

right
The value indicating the amount of left shift or valarray whose elements indicate the element-wise amount of left shift.

Return value

A valarray whose elements have been shifted left the amount specified in right.

Remarks

Signed numbers have their signs preserved.

Example

// valarray_class_op_ls.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 8 ), vaR ( 8 );
   for ( i = 0 ; i < 8 ; i += 2 )
      vaL [ i ] =  1;
   for ( i = 1 ; i < 8 ; i += 2 )
      vaL [ i ] =  -1;
   for ( i = 0 ; i < 8 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial operand valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The  right valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL <<= vaR;
   cout << "The element-by-element result of "
        << "the left shift"
        << endl << "on the operand array is the valarray:"
        << endl << "( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial operand valarray is: ( 1 -1 1 -1 1 -1 1 -1 ).
The  right valarray is: ( 0 1 2 3 4 5 6 7 ).
The element-by-element result of the left shift
on the operand array is the valarray:
( 1 -2 4 -8 16 -32 64 -128 ).

`operator*=`

Multiplies the elements of a specified valarray or a value of the element type, element-wise, to an operand valarray.

valarray<Type>& operator*=(const valarray<Type>& right);

valarray<Type>& operator*=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to multiply, element-wise, the operand valarray.

Return value

A valarray whose elements are the element-wise product of the operand valarray and right.

Example

// valarray_op_emult.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 8 ), vaR ( 8 );
   for ( i = 0 ; i < 8 ; i += 2 )
      vaL [ i ] =  2;
   for ( i = 1 ; i < 8 ; i += 2 )
      vaL [ i ] =  -1;
   for ( i = 0 ; i < 8 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial Right valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL *= vaR;
   cout << "The element-by-element result of "
        << "the multiplication is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}
/* Output:
The initial valarray is: ( 2 -1 2 -1 2 -1 2 -1 ).
The initial Right valarray is: ( 0 1 2 3 4 5 6 7 ).
The element-by-element result of the multiplication is the
valarray: ( 0 -1 4 -3 8 -5 12 -7 ).
*/

`operator+`

A unary operator that applies a plus to each element in a valarray. For normal arithmetic values, this operation has no effect.

valarray<Type> operator+() const;

Return value

A valarray whose elements are the unary plus result of the operand array.

Example

// valarray_op_eplus.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 10 );
   valarray<int> vaPLUS ( 10 );
   for ( i = 0 ; i < 10 ; i += 2 )
      vaL [ i ] =  -i;
   for ( i = 1 ; i < 10 ; i += 2 )
      vaL [ i ] =  i-1;

   cout << "The initial valarray is:  ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   vaPLUS = +vaL;
   cout << "The element-by-element result of "
        << "the operator+ is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaPLUS [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is:  ( 0 0 -2 2 -4 4 -6 6 -8 8 ).
The element-by-element result of the operator+ is the
valarray: ( 0 0 -2 2 -4 4 -6 6 -8 8 ).

`operator+=`

Adds the elements of a specified valarray or a value of the element type, element-wise, to an operand valarray.

valarray<Type>& operator+=(const valarray<Type>& right);

valarray<Type>& operator+=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be added, element-wise, to the operand valarray.

Return value

A valarray whose elements are the element-wise sum of the operand valarray and right.

Example

// valarray_op_eadd.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 8 ), vaR ( 8 );
   for ( i = 0 ; i < 8 ; i += 2 )
      vaL [ i ] =  2;
   for ( i = 1 ; i < 8 ; i += 2 )
      vaL [ i ] =  -1;
   for ( i = 0 ; i < 8 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial valarray is: ( ";
      for (i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial  right valarray is: ( ";
      for (i = 0 ; i < 8 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL += vaR;
   cout << "The element-by-element result of "
        << "the sum is the"
        << endl << "valarray: ( ";
      for (i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is: ( 2 -1 2 -1 2 -1 2 -1 ).
The initial  right valarray is: ( 0 1 2 3 4 5 6 7 ).
The element-by-element result of the sum is the
valarray: ( 2 0 4 2 6 4 8 6 ).

`operator-`

A unary operator that applies an arithmetic negation to each element in a valarray.

valarray<Type> operator-() const;

Return value

A valarray whose elements are arithmetically negated from the elements of the operand valarray.

Example

// valarray_op_eminus.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 10 );
   valarray<int> vaMINUS ( 10 );
   for ( i = 0 ; i < 10 ; i += 2 )
      vaL [ i ] =  -i;
   for ( i = 1 ; i < 10 ; i += 2 )
      vaL [ i ] =  i-1;

   cout << "The initial valarray is:  ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   vaMINUS = -vaL;
   cout << "The element-by-element result of "
        << "the operator- is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaMINUS [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is:  ( 0 0 -2 2 -4 4 -6 6 -8 8 ).
The element-by-element result of the operator- is the
valarray: ( 0 0 2 -2 4 -4 6 -6 8 -8 ).

`operator-=`

Subtracts the elements of a specified valarray or a value of the element type, element-wise, from an operand valarray.

valarray<Type>& operator-=(const valarray<Type>& right);

valarray<Type>& operator-=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be subtracted, element-wise, from the operand valarray.

Return value

A valarray whose elements are the element-wise difference of the operand valarray and right.

Example

// valarray_op_esub.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 8 ), vaR ( 8 );
   for ( i = 0 ; i < 8 ; i += 2 )
      vaL [ i ] =  10;
   for ( i = 1 ; i < 8 ; i += 2 )
      vaL [ i ] =  0;
   for ( i = 0 ; i < 8 ; i++ )
      vaR [ i ] =  i;

   cout << "The initial valarray is: ( ";
      for (i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial  right valarray is: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL -= vaR;
   cout << "The element-by-element result of "
        << "the difference is the"
        << endl << "valarray: ( ";
      for ( i = 0 ; i < 8 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is: ( 10 0 10 0 10 0 10 0 ).
The initial  right valarray is: ( 0 1 2 3 4 5 6 7 ).
The element-by-element result of the difference is the
valarray: ( 10 -1 8 -3 6 -5 4 -7 ).

`operator/=`

Divides an operand valarray element-wise by the elements of a specified valarray or a value of the element type.

valarray<Type>& operator/=(const valarray<Type>& right);

valarray<Type>& operator/=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be divided, element-wise, into the operand valarray.

Return value

A valarray whose elements are the element-wise quotient of the operand valarray divided by right.

Example

// valarray_op_ediv.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<double> vaL ( 6 ), vaR ( 6 );
   for ( i = 0 ; i < 6 ; i += 2 )
      vaL [ i ] =  100;
   for ( i = 1 ; i < 6 ; i += 2 )
      vaL [ i ] =  -100;
   for ( i = 0 ; i < 6 ; i++ )
      vaR [ i ] =  2*i;

   cout << "The initial valarray is: ( ";
      for (i = 0 ; i < 6 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The initial Right valarray is: ( ";
      for (i = 0 ; i < 6 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL /= vaR;
   cout << "The element-by-element result of "
        << "the quotient is the"
        << endl << "valarray: ( ";
      for (i = 0 ; i < 6 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial valarray is: ( 100 -100 100 -100 100 -100 ).
The initial Right valarray is: ( 0 2 4 6 8 10 ).
The element-by-element result of the quotient is the
valarray: ( inf -50 25 -16.6667 12.5 -10 ).

`operator=`

Assigns elements to a valarray whose values are specified either directly or as part of some other valarray or by a slice_array, gslice_array, mask_array, or indirect_array.

valarray<Type>& operator=(const valarray<Type>& right);

valarray<Type>& operator=(valarray<Type>&& right);

valarray<Type>& operator=(const Type& val);

valarray<Type>& operator=(const slice_array<Type>& slicearray);

valarray<Type>& operator=(const gslice_array<Type>& gslicearray);

valarray<Type>& operator=(const mask_array<Type>& maskarray);

valarray<Type>& operator=(const indirect_array<Type>& indarray);

Parameters

right
The valarray to be copied into the operand valarray.

val
The value to be assigned to the elements of the operand valarray.

slicearray
The slice_array to be copied into the operand valarray.

gslicearray
The gslice_array to be copied into the operand valarray.

maskarray
The mask_array to be copied into the operand valarray.

indarray
The indirect_array to be copied into the operand valarray.

Return value

The first member operator replaces the controlled sequence with a copy of the sequence controlled by right.

The second member operator is the same as the first, but with an Rvalue reference declarator: &&.

The third member operator replaces each element of the controlled sequence with a copy of val.

The remaining member operators replace those elements of the controlled sequence selected by their arguments, which are generated only by operator[].

If the value of a member in the replacement controlled sequence depends on a member in the initial controlled sequence, the result is undefined.

Remarks

If the length of the controlled sequence changes, normally the result is undefined. In this implementation, however, the effect is merely to invalidate any pointers or references to elements in the controlled sequence.

Example

// valarray_op_assign.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> va ( 10 ), vaR ( 10 );
   for ( i = 0 ; i < 10 ; i += 1 )
      va [ i ] = i;
   for ( i = 0 ; i < 10 ; i+=1 )
      vaR [ i ] = 10 -  i;

   cout << "The operand valarray va is:";
   for ( i = 0 ; i < 10 ; i++ )
      cout << " " << va [ i ];
   cout << endl;

   cout << "The operand valarray vaR is:";
      for ( i = 0 ; i < 10 ; i++ )
         cout << " " << vaR [ i ];
   cout << endl;

   // Assigning vaR to va with the first member function
   va = vaR;
   cout << "The reassigned valarray va is:";
   for ( i = 0 ; i < 10 ; i++ )
      cout << " " << va [ i ];
   cout << endl;

   // Assigning elements of value 10 to va
   // with the second member function
   va = 10;
   cout << "The reassigned valarray va is:";
      for ( i = 0 ; i < 10 ; i++ )
         cout << " " << va [ i ];
   cout << endl;
}

The operand valarray va is: 0 1 2 3 4 5 6 7 8 9
The operand valarray vaR is: 10 9 8 7 6 5 4 3 2 1
The reassigned valarray va is: 10 9 8 7 6 5 4 3 2 1
The reassigned valarray va is: 10 10 10 10 10 10 10 10 10 10

`operator[]`

Returns a reference to an element or its value at specified index or a specified subset.

Type& operator[](size_t index);

slice_array<Type> operator[](slice slicearray);

gslice_array<Type> operator[](const gslice& gslicearray);

mask_array<Type> operator[](const valarray<bool>& boolarray);

indirect_array<Type> operator[](const valarray<size_t>& indarray);

Type operator[](size_t index) const;

valarray<Type> operator[](slice slicearray) const;

valarray<Type> operator[](const gslice& gslicearray) const;

valarray<Type> operator[](const valarray<bool>& boolarray) const;

valarray<Type> operator[](const valarray<size_t>& indarray) const;

Parameters

index
The index of the element to be assigned a value.

slicearray
A slice_array of a valarray that specifies a subset to be selected or returned to a new valarray.

gslicearray
A gslice_array of a valarray that specifies a subset to be selected or returned to a new valarray.

boolarray
A bool_array of a valarray that specifies a subset to be selected or returned to a new valarray.

indarray
An indirect_array of a valarray that specifies a subset to be selected or returned to a new valarray.

Return value

A reference to an element or its value at specified index or a specified subset.

Remarks

The member operator is overloaded to provide several ways to select sequences of elements from among the ones controlled by *this. The first group of five member operators work together with various overloads of operator= (and other assigning operators) to allow selective replacement (slicing) of the controlled sequence. The selected elements must exist.

When compiled by using _ITERATOR_DEBUG_LEVEL defined as 1 or 2, a runtime error occurs if you attempt to access an element outside the bounds of the valarray. For more information, see Checked iterators.

Example

See the examples for slice::slice and gslice::gslice for an example of how to declare and use operator[].

`operator^=`

Obtains the bitwise exclusive or (^) of a valarray with either a specified valarray or a value of the element type.

valarray<Type>& operator^=(const valarray<Type>& right);

valarray<Type>& operator^=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be combined by the bitwise exclusive or (XOR) operator (^) with the operand valarray.

Return value

A valarray whose elements are the bitwise exclusive or (XOR) of the operand valarray and right.

Remarks

The bitwise exclusive or, referred to as XOR and denoted by operator ^, has the following semantics: Given bits b1 and b2, b1 ^ b2 is 1 if exactly one of the elements is 1, and 0 if both elements are 0 or 1.

Example

// valarray_op_exor.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
    using namespace std;
    int i;

    valarray<int> vaL ( 10 ), vaR ( 10 );
    for ( i = 0 ; i < 10 ; i += 2 )
        vaL [ i ] =  1;
    for ( i = 1 ; i < 10 ; i += 2 )
        vaL [ i ] =  0;
    for ( i = 0 ; i < 10 ; i += 3 )
        vaR [ i ] =  i;
    for ( i = 1 ; i < 10 ; i += 3 )
        vaR [ i ] =  i-1;
    for ( i = 2 ; i < 10 ; i += 3 )
        vaR [ i ] =  i-1;

    cout << "The initial operand valarray is:  ( ";
        for (i = 0 ; i < 10 ; i++ )
            cout << vaL [ i ] << " ";
    cout << ")." << endl;

    cout << "The  right valarray is: ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaR [ i ] << " ";
    cout << ")." << endl;

    vaL ^= vaR;
    cout << "The element-by-element result of "
        << "the bitwise XOR operator^= is the"
        << endl << "valarray: ( ";
        for (i = 0 ; i < 10 ; i++ )
            cout << vaL [ i ] << " ";
    cout << ")." << endl;
}

The initial operand valarray is:  ( 1 0 1 0 1 0 1 0 1 0 ).
The  right valarray is: ( 0 0 1 3 3 4 6 6 7 9 ).
The element-by-element result of the bitwise XOR operator^= is the
valarray: ( 1 0 0 3 2 4 7 6 6 9 ).

`operator|=`

Obtains the bitwise OR (|) of elements in an array either with the corresponding elements in a specified valarray or with a value of the element type.

valarray<Type>& operator|=(const valarray<Type>& right);

valarray<Type>& operator|=(const Type& right);

Parameters

right
The valarray or value of an element type identical to that of the operand valarray that is to be combined, element-wise, by the bitwise OR (|) with the operand valarray.

Return value

A valarray whose elements are the element-wise bitwise OR (|) of the operand valarray by right.

Remarks

A bitwise operation can only be used to manipulate bits in integral data types such as char and int. It doesn't work on float, double, long double, void, bool, or other, more complex data types.

The bitwise OR (|) applies to the data type on the level of the individual bits. Given bits b1 and b2, b1 | b2 is 1 if at least one of the bits is 1; 0 if both bits are 0.

Example

// valarray_class_op_bitor.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> vaL ( 10 ), vaR ( 10 );
   for ( i = 0 ; i < 10 ; i += 2 )
      vaL [ i ] =  1;
   for ( i = 1 ; i < 10 ; i += 2 )
      vaL [ i ] =  0;
   for ( i = 0 ; i < 10 ; i += 3 )
      vaR [ i ] =  i;
   for ( i = 1 ; i < 10 ; i += 3 )
      vaR [ i ] =  i-1;
   for ( i = 2 ; i < 10 ; i += 3 )
      vaR [ i ] =  i-1;

   cout << "The initial operand valarray is:"
        << endl << "( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;

   cout << "The  right valarray is:"
        << endl << "( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << vaR [ i ] << " ";
   cout << ")." << endl;

   vaL |= vaR;
   cout << "The element-by-element result of "
        << "the bitwise OR"
        << endl << "operator|= is the valarray:"
        << endl << "( ";
      for (i = 0 ; i < 10 ; i++ )
         cout << vaL [ i ] << " ";
   cout << ")." << endl;
}

The initial operand valarray is:
( 1 0 1 0 1 0 1 0 1 0 ).
The  right valarray is:
( 0 0 1 3 3 4 6 6 7 9 ).
The element-by-element result of the bitwise OR
operator|= is the valarray:
( 1 0 1 3 3 4 7 6 7 9 ).

`operator~`

A unary operator that obtains the bitwise complement of values of each element in a valarray.

valarray<Type> operator~() const;

Return value

The valarray of values that are the unary bitwise complement of the element values of the operand valarray.

Remarks

A bitwise operation can only manipulate bits in integral types, such as char and int. It doesn't work on float, double, long double, void, bool, or other, more complex data types.

The unary bitwise complement operator ~ applies to the data type at the level of the individual bits. Given bit b, ~b is 1 if b is 0 and 0 if b is 1.

Example

// valarray_op_bitnot.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
    using namespace std;
    int i;

    valarray<unsigned short int> vaL1 ( 10 );
    valarray<unsigned short int> vaNOT1 ( 10 );
    for ( i = 0 ; i < 10 ; i += 2 )
        vaL1 [ i ] =  i;
    for ( i = 1 ; i < 10 ; i += 2 )
        vaL1 [ i ] =  5*i;

    cout << "The initial valarray <unsigned short int> is:  ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaL1 [ i ] << " ";
    cout << ")." << endl;

    vaNOT1 = ~vaL1;
    cout << "The element-by-element result of "
        << "the bitwise NOT operator~ is the"
        << endl << "valarray: ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaNOT1 [ i ] << " ";
    cout << ")." << endl << endl;

    valarray<int> vaL2 ( 10 );
    valarray<int> vaNOT2 ( 10 );
    for ( i = 0 ; i < 10 ; i += 2 )
        vaL2 [ i ] =  i;
    for ( i = 1 ; i < 10 ; i += 2 )
        vaL2 [ i ] =  -2 * i;

    cout << "The initial valarray <int> is:  ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaL2 [ i ] << " ";
    cout << ")." << endl;

    vaNOT2 = ~vaL2;
    cout << "The element-by-element result of "
        << "the bitwise NOT operator~ is the"
        << endl << "valarray: ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaNOT2 [ i ] << " ";
    cout << ")." << endl;

    // The negative numbers are represented using
    // the two's complement approach, so adding one
    // to the flipped bits returns the negative elements
    vaNOT2 = vaNOT2 + 1;
    cout << "The element-by-element result of "
        << "adding one"
        << endl << "is the negative of the "
        << "original elements the"
        << endl << "valarray: ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << vaNOT2 [ i ] << " ";
    cout << ")." << endl;
}

The initial valarray <unsigned short int> is:  ( 0 5 2 15 4 25 6 35 8 45 ).
The element-by-element result of the bitwise NOT operator~ is the
valarray: ( 65535 65530 65533 65520 65531 65510 65529 65500 65527 65490 ).

The initial valarray <int> is:  ( 0 -2 2 -6 4 -10 6 -14 8 -18 ).
The element-by-element result of the bitwise NOT operator~ is the
valarray: ( -1 1 -3 5 -5 9 -7 13 -9 17 ).
The element-by-element result of adding one
is the negative of the original elements the
valarray: ( 0 2 -2 6 -4 10 -6 14 -8 18 ).

`resize`

Changes the number of elements in a valarray to a specified number.

void resize(
    size_t new_size);

void resize(
    size_t new_size,
    const Type val);

Parameters

new_size
The number of elements in the resized valarray.

val
The value to be given to the elements of the resized valarray.

Remarks

The first member function initializes elements with their default constructor.

Any pointers or references to elements in the controlled sequence are invalidated.

Example

The following example demonstrates the use of the valarray::resize member function.

// valarray_resize.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main()
{
    using namespace std;
    int i;
    size_t size1, sizeNew;

    valarray<int> va1(10);
    for (i = 0; i < 10; i+=1)
        va1[i] = i;

    cout << "The valarray contains ( ";
        for (i = 0; i < 10; i++)
            cout << va1[i] << " ";
    cout << ")." << endl;

    size1 = va1.size();
    cout << "The number of elements in the valarray is: "
         << size1  << "." <<endl << endl;

    va1.resize(15, 10);

    cout << "The valarray contains ( ";
        for (i = 0; i < 15; i++)
            cout << va1[i] << " ";
    cout << ")." << endl;
    sizeNew = va1.size();
    cout << "The number of elements in the resized valarray is: "
         << sizeNew  << "." <<endl << endl;
}

The valarray contains ( 0 1 2 3 4 5 6 7 8 9 ).
The number of elements in the valarray is: 10.

The valarray contains ( 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 ).
The number of elements in the resized valarray is: 15.

`shift`

Shifts all the elements in a valarray by a specified number of places.

valarray<Type> shift(int count) const;

Parameters

count
The number of places the elements are to be shifted forward.

Return value

A new valarray in which all the elements have been moved count positions toward the front of the valarray, or leftward when compared to their positions in the operand valarray.

Remarks

A positive value of count shifts the elements left count places, with zero fill.

A negative value of count shifts the elements right count places, with zero fill.

Example

// valarray_shift.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
   using namespace std;
   int i;

   valarray<int> va1 ( 10 ), va2 ( 10 );
   for ( i = 0 ; i < 10 ; i += 1 )
      va1 [ i ] =  i;
   for ( i = 0 ; i < 10 ; i += 1 )
      va2 [ i ] = 10 -  i;

   cout << "The operand valarray va1(10) is: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << va1 [ i ] << " ";
   cout << ")." << endl;

   // A positive parameter shifts elements left
   va1 = va1.shift ( 4 );
   cout << "The shifted valarray va1 is: va1.shift (4) = ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << va1 [ i ] << " ";
   cout << ")." << endl;

   cout << "The operand valarray va2(10) is: ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << va2 [ i ] << " ";
   cout << ")." << endl;

   // A negative parameter shifts elements right
   va2 = va2.shift ( - 4 );
   cout << "The shifted valarray va2 is: va2.shift (-4) = ( ";
      for ( i = 0 ; i < 10 ; i++ )
         cout << va2 [ i ] << " ";
   cout << ")." << endl;
}

The operand valarray va1(10) is: ( 0 1 2 3 4 5 6 7 8 9 ).
The shifted valarray va1 is: va1.shift (4) = ( 4 5 6 7 8 9 0 0 0 0 ).
The operand valarray va2(10) is: ( 10 9 8 7 6 5 4 3 2 1 ).
The shifted valarray va2 is: va2.shift (-4) = ( 0 0 0 0 10 9 8 7 6 5 ).

`size`

Finds the number of elements in a valarray.

size_t size() const;

Return value

The number of elements in the operand valarray.

Example

The following example demonstrates the use of the valarray::size member function.

// valarray_size.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main()
{
    using namespace std;
    int i;
    size_t size1, size2;

    valarray<int> va1(10), va2(12);
    for (i = 0; i < 10; i += 1)
        va1[i] =  i;
    for (i = 0; i < 10; i += 1)
        va2[i] =  i;

    cout << "The operand valarray va1(10) is: ( ";
        for (i = 0; i < 10; i++)
            cout << va1[i] << " ";
    cout << ")." << endl;

    size1 = va1.size();
    cout << "The number of elements in the valarray va1 is: va1.size = "
         << size1  << "." <<endl << endl;

    cout << "The operand valarray va2(12) is: ( ";
        for (i = 0; i < 10; i++)
            cout << va2[i] << " ";
    cout << ")." << endl;

    size2 = va2.size();
    cout << "The number of elements in the valarray va2 is: va2.size = "
         << size2  << "." << endl << endl;

    // Initializing two more elements to va2
    va2[10] = 10;
    va2[11] = 11;
    cout << "After initializing two more elements,\n"
         << "the operand valarray va2(12) is now: ( ";
        for (i = 0; i < 12; i++)
            cout << va2[i] << " ";
    cout << ")." << endl;
    cout << "The number of elements in the valarray va2 is still: "
         << size2  << "." << endl;
}

The operand valarray va1(10) is: ( 0 1 2 3 4 5 6 7 8 9 ).
The number of elements in the valarray va1 is: va1.size = 10.

The operand valarray va2(12) is: ( 0 1 2 3 4 5 6 7 8 9 ).
The number of elements in the valarray va2 is: va2.size = 12.

After initializing two more elements,
the operand valarray va2(12) is now: ( 0 1 2 3 4 5 6 7 8 9 10 11 ).
The number of elements in the valarray va2 is still: 12.

`sum`

Determines the sum of all the elements in a valarray of nonzero length.

Type sum() const;

Return value

The sum of the elements of the operand valarray.

Remarks

If the length is greater than one, the member function adds values to the sum by applying operator+= between pairs of elements of class Type. It means the operator needs be provided for elements of type Type.

Example

// valarray_sum.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
    using namespace std;
    int i;
    int sumva = 0;

    valarray<int> va ( 10 );
    for ( i = 0 ; i < 10 ; i+=1 )
        va [ i ] =  i;

    cout << "The operand valarray va (10) is: ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << va [ i ] << " ";
    cout << ")." << endl;

    sumva = va.sum ( );
    cout << "The sum of elements in the valarray is: "
        << sumva  << "." <<endl;
}

The operand valarray va (10) is: ( 0 1 2 3 4 5 6 7 8 9 ).
The sum of elements in the valarray is: 45.

`swap`

Exchanges the elements of two valarray objects.

void swap(valarray& right);

Parameters

right
A valarray providing the elements to be swapped.

Remarks

The member function swaps the controlled sequences between *this and right. It does so in constant time, it throws no exceptions, and it invalidates no references, pointers, or iterators to elements in the two controlled sequences.

`valarray`

Constructs a valarray of a specific size or with elements of a specific value or as a copy of another valarray or subset of another valarray.

valarray();

explicit valarray(
    size_t count);

valarray(
    const Type& val,
    size_t count);

valarray(
    const Type* ptr,
    size_t count);

valarray(
    const valarray<Type>& right);

valarray(
    const slice_array<Type>& sliceArray);

valarray(
    const gslice_array<Type>& gsliceArray);

valarray(
    const mask_array<Type>& maskArray);

valarray(
    const indirect_array<Type>& indArray);

valarray(
    valarray<Type>&& tight);

valarray(
    initializer_list<Type> iList);

Parameters

count
The number of elements to be in the valarray.

val
The value to be used in initializing the elements in the valarray.

ptr
Pointer to the values to be used to initialize the elements in the valarray.

right
An existing valarray to initialize the new valarray.

sliceArray
A slice_array whose element values are to be used in initializing the elements of the valarray being constructed.

gsliceArray
A gslice_array whose element values are to be used in initializing the elements of the valarray being constructed.

maskArray
A mask_array whose element values are to be used in initializing the elements of the valarray being constructed.

indArray
A indirect_array whose element values are to be used in initializing the elements of the valarray being constructed.

iList
The initializer_list containing the elements to copy.

Remarks

The first (default) constructor initializes the object to an empty valarray. The next three constructors each initialize the object to a valarray of count elements as follows:

For explicit valarray(size_t count), each element is initialized with the default constructor.
For valarray(const Type& val, count), each element is initialized with val.
For valarray(const Type* ptr, count), the element at position I is initialized with ptr[I].

Each remaining constructor initializes the object to a valarray<Type> object determined by the subset specified in the argument.

The last constructor is the same as the next to last, but with an Rvalue reference declarator: &&.

Example

// valarray_ctor.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main()
{
    using namespace std;
    int i;

    // The second member function
    valarray<int> va(10);
    for (auto i : va){
        va[i] = 2 * (i + 1);
    }

    cout << "The operand valarray va is:\n(";
    for (auto i : va) {
        cout << " " << va[i];
    }
    cout << " )" << endl;

    slice Slice(2, 4, 3);

    // The fifth member function
    valarray<int> vaSlice = va[Slice];

    cout << "The new valarray initialized from the slice is vaSlice =\n"
        << "va[slice( 2, 4, 3)] = (";
    for (int i = 0; i < 3; i++) {
        cout << " " << vaSlice[i];
    }
    cout << " )" << endl;

    valarray<int> va2{{ 1, 2, 3, 4 }};
    for (auto& v : va2) {
        cout << v << " ";
    }
    cout << endl;
}

The operand valarray va is:
( 0 2 2 2 2 2 2 2 2 2 )
The new valarray initialized from the slice is vaSlice =
va[slice( 2, 4, 3)] = ( 0 0 0 )
1 2 3 4

`value_type`

A type that represents the type of element stored in a valarray.

typedef Type value_type;

Remarks

The type is a synonym for the template parameter Type.

Example

// valarray_value_type.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>

int main( )
{
    using namespace std;
    int i;
    valarray<int> va ( 10 );
    for ( i = 0 ; i < 10 ; i += 2 )
        va [ i ] =  i;
    for ( i = 1 ; i < 10 ; i += 2 )
        va [ i ] =  -1;

    cout << "The initial operand valarray is:  ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << va [ i ] << " ";
    cout << ")." << endl;

    // value_type declaration and initialization:
    valarray<int>::value_type Right = 10;

    cout << "The declared value_type Right is: "
            << Right << endl;
    va *= Right;
    cout << "The resulting valarray is:  ( ";
        for ( i = 0 ; i < 10 ; i++ )
            cout << va [ i ] << " ";
    cout << ")." << endl;
}

The initial operand valarray is:  ( 0 -1 2 -1 4 -1 6 -1 8 -1 ).
The declared value_type Right is: 10
The resulting valarray is:  ( 0 -10 20 -10 40 -10 60 -10 80 -10 ).

แชร์ผ่าน

valarray class

Remarks

Members

Constructors

Typedefs

Functions

Operators

apply

Parameters

Return value

Remarks

Example

cshift

Parameters

Return value

Remarks

Example

free

Remarks

max

Return value

Remarks

Example

min

Return value

Remarks

Example

operator!

Return value

Remarks

Example

operator%=

Parameters

Return value

Example

operator&=

Parameters

Return value

Remarks

Example

operator>>=

Parameters

Return value

Remarks

Example

operator<<=

Parameters

Return value

Remarks

Example

operator*=

Parameters

Return value

Example

operator+

Return value

Example

operator+=

Parameters

Return value

Example

operator-

Return value

Example

operator-=

Parameters

Return value

Example

operator/=

Parameters

Return value

Example

operator=

Parameters

Return value

Remarks

Example

operator[]

Parameters

`valarray` class

`apply`

`cshift`

`free`

`max`

`min`

`operator!`

`operator%=`

`operator&=`

`operator>>=`

`operator<<=`

`operator*=`

`operator+`

`operator+=`

`operator-`

`operator-=`

`operator/=`

`operator=`

`operator[]`

`operator^=`

`operator|=`

`operator~`

`resize`

`shift`

`size`

`sum`

`swap`

`valarray`

`value_type`