1. 简介
在头文件
<numeric>中。
| 函数 | 作用 | 文档 |
|---|---|---|
accumulate(beg,end,val) |
对[beg,end)内元素之和，加到初始值val上。 |
accumulate() |
accumulate(beg,end,val,binary) |
将函数binary代替加法运算，执行accumulate()。 |
accumulate() |
partial_sum(beg,end,res) |
将[beg,end)内该位置前所有元素之和放进res中。 |
partial_sum() |
partial_sum(beg,end,res,binary) |
将函数binary代替加法运算，执行partial_sum()。 |
partial_sum() |
adjacent_difference(beg1,end1,res) |
将[beg,end)内每个新值代表当前元素与上一个元素的差放进res中。 |
adjacent_difference() |
adjacent_difference(beg1,end1,res,binary) |
将函数binary代替减法运算，执行adjacent_difference()。 |
adjacent_difference() |
inner_product(beg1,end1,beg2,val) |
对两个序列做内积(对应元素相乘，再求和)并将内积加到初始值val上。 |
inner_product() |
inner_product(beg1,end1,beg2,val,binary1,binary2) |
将函数binary1代替加法运算,将binary2代替乘法运算，执行inner_product()。 |
inner_product() |
2. 示例代码
- accumulate
// accumulate example
#include <iostream> // std::cout
#include <functional> // std::minus
#include <numeric> // std::accumulate
int myfunction (int x, int y) {return x+2*y;}
struct myclass {
int operator()(int x, int y) {return x+3*y;}
} myobject;
int main () {
int init = 100;
int numbers[] = {10,20,30};
std::cout << "using default accumulate: ";
std::cout << std::accumulate(numbers,numbers+3,init);
std::cout << '\n';
std::cout << "using functional's minus: ";
std::cout << std::accumulate (numbers, numbers+3, init, std::minus<int>());
std::cout << '\n';
std::cout << "using custom function: ";
std::cout << std::accumulate (numbers, numbers+3, init, myfunction);
std::cout << '\n';
std::cout << "using custom object: ";
std::cout << std::accumulate (numbers, numbers+3, init, myobject);
std::cout << '\n';
return 0;
}
- partial_sum
// partial_sum example
#include <iostream> // std::cout
#include <functional> // std::multiplies
#include <numeric> // std::partial_sum
int myop (int x, int y) {return x+y+1;}
int main () {
int val[] = {1,2,3,4,5};
int result[5];
std::partial_sum (val, val+5, result);
std::cout << "using default partial_sum: ";
for (int i=0; i<5; i++) std::cout << result[i] << ' ';
std::cout << '\n';
std::partial_sum (val, val+5, result, std::multiplies<int>());
std::cout << "using functional operation multiplies: ";
for (int i=0; i<5; i++) std::cout << result[i] << ' ';
std::cout << '\n';
std::partial_sum (val, val+5, result, myop);
std::cout << "using custom function: ";
for (int i=0; i<5; i++) std::cout << result[i] << ' ';
std::cout << '\n';
return 0;
}
- adjacent_difference
// adjacent_difference example
#include <iostream> // std::cout
#include <functional> // std::multiplies
#include <numeric> // std::adjacent_difference
int myop (int x, int y) {return x+y;}
int main () {
int val[] = {1,2,3,5,9,11,12};
int result[7];
std::adjacent_difference (val, val+7, result);
std::cout << "using default adjacent_difference: ";
for (int i=0; i<7; i++) std::cout << result[i] << ' ';
std::cout << '\n';
std::adjacent_difference (val, val+7, result, std::multiplies<int>());
std::cout << "using functional operation multiplies: ";
for (int i=0; i<7; i++) std::cout << result[i] << ' ';
std::cout << '\n';
std::adjacent_difference (val, val+7, result, myop);
std::cout << "using custom function: ";
for (int i=0; i<7; i++) std::cout << result[i] << ' ';
std::cout << '\n';
return 0;
}
- inner_product
// inner_product example
#include <iostream> // std::cout
#include <functional> // std::minus, std::divides
#include <numeric> // std::inner_product
int myaccumulator (int x, int y) {return x-y;}
int myproduct (int x, int y) {return x+y;}
int main () {
int init = 100;
int series1[] = {10,20,30};
int series2[] = {1,2,3};
std::cout << "using default inner_product: ";
std::cout << std::inner_product(series1,series1+3,series2,init);
std::cout << '\n';
std::cout << "using functional operations: ";
std::cout << std::inner_product(series1,series1+3,series2,init,
std::minus<int>(),std::divides<int>());
std::cout << '\n';
std::cout << "using custom functions: ";
std::cout << std::inner_product(series1,series1+3,series2,init,
myaccumulator,myproduct);
std::cout << '\n';
return 0;
}
