STL 之for_each,transform

返回

for_each：对指定区间中的每个元素使用指定的函数进行访问及处理，所用的函数作为参数传递给该函数。

transform：元素传输

声明：

#include <algorithm>
template <class inputItr,class function>
function for_each(inputItr first,inputItr last,function func);

template <class inputItr, class outputItr, class unaryOperation>
outputItr transform(inputItr first,inputItr last, outputItr destFirst,unaryOperation op);

template <class inputItr1, class inputItr2, class outputItr, class binaryOperation>
outputItr transform(inputItr1 first1, inputItr1 last, inputItr2 first2, outputItr destFirst,binaryOperation bop);

示例代码：

#include <iostream>
#include <list>

#include <string>
#include <numeric>
#include <iterator>
#include <vector>
#include <functional>

#include <algorithm>

using namespace std;

void doubleNum(int& num) {
	num = 2 * num;
	cout << num << " ";
}

int main() {
	char cList[5] = {'a','b','c','d','e'};
	vector<char> charList(cList,cList+5);
	ostream_iterator<char> sreen(cout, " ");

	cout << "charList:" << endl;
	copy(charList.begin(),charList.end(),sreen);
	cout << endl;

	//transform
	transform(charList.begin(),charList.end(),charList.begin(),toupper);
	cout << "charList:" << endl;
	copy(charList.begin(),charList.end(),sreen);
	cout << endl;

	int list[7] = {2,8,5,1,7,11,3};
	ostream_iterator<int> srceenInt(cout, " ");
	cout << "list" << endl;
	copy(list,list+7,srceenInt);
	cout << endl;

	// for_each
	for_each(list,list + 7, doubleNum);
	cout << endl;

	cout << "list" << endl;
	copy(list,list+7,srceenInt);
	cout << endl;
	
	return 0;
}

运行结果：

charList:
a b c d e
charList:
A B C D E
list
2 8 5 1 7 11 3
4 16 10 2 14 22 6
list
4 16 10 2 14 22 6