Valarray Library Learning

c++ There are three classes in the form of standard library table array ：array： Fixed length , The purpose is to replace the built-in array, such as : int a[5] = {1,3,5,7,9};vector： Support variable length classes , valarray： Is a class that represents and operates on an array of values , Design for numerical computation , Support mathematical operations on elements , And support various forms of generalized subscript operators 、 Slicing and indirect access .
So let's see valarray Use example of :

Member functions

( Constructors )	Construct a new numeric array ( Expose member functions )
( Destructor )	Destruct an array of values ( Expose member functions )
operator=	Assign value to content ( Expose member functions )
operator[]	obtain / Set up valarray Array elements 、 Slice or mask ( Expose member functions )
operator+ operator- operator~ operator!	Yes valarray Use unary arithmetic operators for each element of ( Expose member functions )
operator+= operator-= operator*= operator/= operator%= operator&= operator|= operator^= operator<<= operator>>=	Yes valarray Apply the compound assignment operator to each element of ( Expose member functions )
swap	With another valarray In exchange for ( Expose member functions )
size	return valarray Size ( Expose member functions )
resize	change valarray Size ( Expose member functions )
sum	Calculate the sum of all elements ( Expose member functions )
min	Returns the smallest element ( Expose member functions )
max	Returns the largest element ( Expose member functions )
shift	Move by filling in zero valarray The elements of ( Expose member functions )
cshift	Cyclic movement valarray The elements of ( Expose member functions )
apply	Yes valarray Each element of the application function ( Expose member functions )

1.valarray initialization

#include <iostream>
#include <valarray>

using namespace std;

// Output valarray
template <typename T>
void outValarray(const valarray<T>& val)
{
    for(auto v: val)
        cout << v << "\t";
    cout << endl;
}

int main()
{
    //1. Create a size of 5 Of valarray
    valarray<int> val(5);
    outValarray(val);

    //2. Use list {1,3,5,7,9} Initialize a valarray
    valarray<int> val2 = {1,3,5,7,9};
    outValarray(val2);

    //3. Create a size of 5, It's worth it all 7 Of valarray
    valarray<int> val3(7, 5);
    outValarray(val3);

    //4. Initialize with an array valarray
    int ia[] = {10,20,30,40,50};
    valarray<int> val4(ia, sizeof(ia)/sizeof(ia[0]));
    outValarray(val4);

    //5. Use an array to create a size of 3 Of valarray
    valarray<int> val5(ia + 2, 3);
    outValarray(val5);

    //6. Use valarray Do math 
    val = (val2 + val4)*val4;
    outValarray(val);

    cout << "Hello World!" << endl;
    return 0;
}

Running results ：

2.valarray Unary arithmetic operation ：

#include <iostream>
#include <valarray>

using namespace std;

// Output valarray
template <typename T>
void outValarray(const valarray<T>& val)
{
    for(auto v: val)
        cout << v << "\t";
    cout << endl;
}

int main()
{
    //1.operator+ operation , Give each element +11
    valarray<int> val = {1,3,5,7,9};
    outValarray(val);
    val = val + 11;
    outValarray(val);

    //2.operator- operation , Give each element -5
    val = val - 5;
    outValarray(val);

    //3.operator~ operation , Give each element ~
    val = ~val;
    outValarray(val);

    //4.operator ！ operation , Give each element ！
    outValarray(!val);
    cout << "Hello World!" << endl;
    return 0;
}

Running results ：

 3. Yes valarray Apply the compound assignment operator to each element of ：

#include <iostream>
#include <valarray>

using namespace std;

// Output valarray
template <typename T>
void outValarray(const valarray<T>& val)
{
    for(auto v: val)
        cout << v << "\t";
    cout << endl;
}

int main()
{
    //1. operator+= operation 
    valarray<int> val = {1,3,5,7,9};
    outValarray(val);
    val += 11;
    outValarray(val);
    //2. operator-= operation 
    val -= 2;
    outValarray(val);
    //3. operator*= operation 
    val *= 3;
    outValarray(val);
    //4. operator/= operation 
    val /= 2;
    outValarray(val);
    //5. operator%= operation 
    val %= 5;
    outValarray(val);
    //6. operator&= operation 
    val &= 5;
    outValarray(val);
    //7. operator|= operation 
    val |= 1;
    outValarray(val);
    //8. operator^= operation 
    val ^= 2;
    outValarray(val);
    //9. operator<<= operation 
    val <<= 2;
    outValarray(val);
    //10. operator>>= operation 
    val >>= 1;
    outValarray(val);

    cout << "Hello World!" << endl;
    return 0;
}

Calculation results ：

 4. Use examples of member functions ：

#include <iostream>
#include <valarray>

using namespace std;

// Output valarray
template <typename T>
void outValarray(const valarray<T>& val)
{
    for(auto v: val)
        cout << v << "\t";
    cout << endl;
}

int main()
{
    //1.swap  With another  valarray  In exchange for 
    valarray<int> val0 = {1,3,5,7,9};
    valarray<int> val1 = {11,31,51,71,91};
    outValarray(val0);
    outValarray(val1);
    val0.swap(val1);
    cout << endl;
    outValarray(val0);
    outValarray(val1);
    cout << endl;
    //2.size return valarray Size 
    valarray<int> val2 = {1,3,5,7,9,11,13,15};
    cout << "val2.size===== "  << val2.size() << endl;
    cout << endl;
    //3.resize  change  valarray  Size 
    valarray<int> val3 = {1,3,5};
    outValarray(val3);
    val3.resize(5);
    outValarray(val3);
    val3.resize(6, 10);
    outValarray(val3);
    cout << endl;
    //4.sum  Calculate the sum of all elements 
    valarray<int> val = {13,33,59,72,95,11,13,15};
    outValarray(val);
    cout << "val.sum===== "  << val.sum() << endl;
    cout << endl;

    //5.min Returns the smallest element 
    cout << "val.min===== "  << val.min() << endl;
    cout << endl;
    //6.max Returns the largest element 
    cout << "val.max===== "  << val.max() << endl;
    cout << endl;

    //7.shift	 Move by filling in zero  valarray  The elements of 
    valarray<int> val4 = {13,33,59,72,95,11,15};
    outValarray(val4);
    valarray<int> val5 = val4.shift(3);
    outValarray(val5);
    cout << endl;

    //8.cshift  Cyclic movement  valarray  The elements of 
    valarray<int> val6 = {13,33,59,72,95,11,15};
    outValarray(val6);
    valarray<int> val7 = val6.cshift(3);
    outValarray(val7);
    cout << endl;

    //9.apply Yes  valarray  Each element of the application function 
    valarray<int> val8 = {3,32,59,72,95,11,15};
    outValarray(val8);
    val8 = val8.apply([](int n)->int{return n*2;});
    outValarray(val8);
    cout << "Hello World!" << endl;
    return 0;
}

Running results ：

Reference resources ：

Standard library header file <valarray> - cppreference.com