一：功能

        iota 是给定一个初始元素，然后依次对序列中每个元素进行递增++操作，详见代码一；

        atoi 是将字符串转换成整数；atol, atoll 将字符串转换成长整型数 long，long long。

二：用法

<code>#include <iostream>

#include <vector>

#include <numeric>

int main() {

std::vector<int> data(9, 0);

for (auto v : data)

std::cout << v << " ";

std::cout << "\n";

//对序列中元素进行累加， -4是初始值

std::iota(data.begin(), data.end(), -4);

for (auto v : data)

std::cout << v << " ";

std::cout << "\n";

//4 -3 -2 -1 0 1 2 3 4

}

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

printf("%i\n", atoi(" -123junk"));

printf("%i\n", atoi(" +321dust"));

printf("%i\n", atoi("0"));

printf("%i\n", atoi("0042")); // treated as a decimal number with leading zeros

printf("%i\n", atoi("0x2A")); // only leading zero is converted discarding "x2A"

printf("%i\n", atoi("junk")); // no conversion can be performed

printf("%i\n", atoi("2147483648")); // UB: out of range of int

}