for range

#include <iostream>

int main() {
　　int v[] = {1, 2, 3, 4, 5};

　　for(auto& x:v)
　　　　std::cout<<x<<" ";
　　std::cout<<std::endl;

　　return 0;
}

We use auto where we don't have a specific reason to mention the type explicitly.

This is especially important in generic programming where the exact type of an boject

can be hard for the programmer to know and the type names can be quite long.

Auto is a placeholder for the type of the initializer.

The range-for-statement can be read as "for every element of v, from the first to the last, place a

reference to it and print it."

在go语言中实现同样功能：

package main

import "fmt"

func main() {
　　var vec = []int{1, 2, 3, 4, 5}

　　for _, val := range vec {
　　　　fmt.Printf("%d ", val)
　　}
　　fmt.Println()
}

_代表忽略索引，val取索引对应的值。[]int使用的是go语言的切片，Go语言中的循环只有for语句。

#!/usr/bin/python3

print([i for i in range(1, 11) if i % 2 == 0])

Python语言中的列表推导式如上，打印出1到10之间的偶数。