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std::inner_product

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< cpp‎ | algorithm

 
 
アルゴリズムライブラリ
機能します
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Functions
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シーケンス動作を非改変
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Non-modifying sequence operations
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シーケンス動作を変更する
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Modifying sequence operations
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操作を仕切る
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Partitioning operations
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(ソートされた範囲で)ソート操作
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Sorting operations (on sorted ranges)
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バイナリ検索操作(ソート範囲で)
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Binary search operations (on sorted ranges)
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(ソートされた範囲で)操作を設定します
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Set operations (on sorted ranges)
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ヒープ操作
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Heap operations
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最小値/最大値操作
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Minimum/maximum operations
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数値演算
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Numeric operations
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iota(C++11)
accumulate
inner_product
Cライブラリ
Original:
C library
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Defined in header <numeric>
template< class InputIt1, class InputIt2, class T >

T inner_product( InputIt1 first1, InputIt1 last1,

                 InputIt2 first2, T value );
(1)
template<

    class InputIt1,
    class InputIt2,
    class T,
    class BinaryOperation1,
    class BinaryOperation2
> T inner_product( InputIt1 first1, InputIt1 last1,
                   InputIt2 first2, T value,
                   BinaryOperation1 op1,

                   BinaryOperation2 op2 );
(2)
レンジ[first1, last1)first2で別の範囲の始まりの内積(全商品の数すなわち和)を計算する。最初のバージョンは、製品を総括する要素のペアとoperator*の積を計算しoperator+使用して、2番目のバージョンは、それぞれとop2これらのタスクにop1を使用しています.
Original:
Computes inner product (i.e. sum of products) of the range [first1, last1) and another range beginning at first2. The first version uses operator* to compute product of the element pairs and operator+ to sum up the products, the second version uses op2 and op1 for these tasks respectively.
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目次

[編集] パラメータ

first1, last1 -
最初の要素の範囲
Original:
the first range of elements
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first2 -
要素の第2の範囲の始まり
Original:
the beginning of the second range of elements
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value -
積の和の初期値
Original:
initial value of the sum of the products
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op1 - binary operation function object that will be applied.
この関数は、OP2によって返される値とアキュムレータの現在の値を取得し、アキュムレータに格納する新しい値を生成します.
Original:
This function takes a value returned by op2 and the current value of the accumulator and produces a new value to be stored in the accumulator.
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The signature of the function should be equivalent to the following:

 Ret fun(const Type1 &a, const Type2 &b);

The signature does not need to have const &.
The types  Type1 and  Type2 must be such that objects of types T and Type3 can be implicitly converted to  Type1 and  Type2 respectively. The type  Ret must be such that an object of type T can be assigned a value of type  Ret. ​

op2 - binary operation function object that will be applied.
この関数は、各範囲から1つの値をとり、新しい値を生成します.
Original:
This function takes one value from each range and produces a new value.
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The signature of the function should be equivalent to the following:

 Ret fun(const Type1 &a, const Type2 &b);

The signature does not need to have const &.
The types  Type1 and  Type2 must be such that objects of types InputIt1 and InputIt2 can be dereferenced and then implicitly converted to  Type1 and  Type2 respectively. The type  Ret must be such that an object of type Type3 can be assigned a value of type  Ret. ​

Type requirements
-
InputIt1, InputIt2 must meet the requirements of InputIterator.
-
T must meet the requirements of CopyAssignable and CopyConstructible.

[編集] 値を返します

2範囲の内積.
Original:
The inner product of two ranges.
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[編集] 可能な実装

First version
template<class InputIt1, class InputIt2, class T>
T inner_product(InputIt1 first1, InputIt1 last1,
                InputIt2 first2, T value)
{
    while (first1 != last1) {
         value = value + *first1 * *first2;
         ++first1;
         ++first2;
    }
    return value;
}
Second version
template<class InputIt1, class InputIt2,
         class T,
         class BinaryOperation1, class BinaryOperation2>
T inner_product(InputIt1 first1, InputIt1 last1,
                InputIt2 first2, T value,
                BinaryOperation1 op1
                BinaryOperation2 op2)
{
    while (first1 != last1) {
         value = op1(value, op2(*first1, *first2));
         ++first1;
         ++first2;
    }
    return value;
}

[編集]

#include <numeric>
#include <iostream>
#include <vector>
#include <functional>
int main()
{
    std::vector<int> a{0, 1, 2, 3, 4};
    std::vector<int> b{5, 4, 2, 3, 1};
 
    int r1 = std::inner_product(a.begin(), a.end(), b.begin(), 0);
    std::cout << "Inner product of a and b: " << r1 << '\n';
 
    int r2 = std::inner_product(a.begin(), a.end(), b.begin(), 0,
                                std::plus<int>(), std::equal_to<int>());
    std::cout << "Number of pairwise matches between a and b: " <<  r2 << '\n';
}

Output:

Inner product of a and b: 21
Number of pairwise matches between a and b: 2

[編集] も参照してください

要素の範囲をまとめている
Original:
sums up a range of elements
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(関数テンプレート) [edit]
要素の範囲の部分和を計算します
Original:
computes the partial sum of a range of elements
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(関数テンプレート) [edit]