Range {.en}

Range 遍历 {.zh}

::: {.en} range iterates over elements in a variety of data structures. Let’s see how to use range with some of the data structures we’ve already learned. :::

::: {.zh}

range 遍历各种数据结构中的元素。让我们看看如何将 range 用在我们已经学过的一些数据结构。

:::

package main
import "fmt"
func main() {

::: {.en} Here we use range to sum the numbers in a slice. Arrays work like this too. :::

::: {.zh}

在这里，我们使用 range 来对 slice 中的数字求和。对数组也可以采用这种方法。

:::

    nums := []int{2, 3, 4}
    sum := 0
    for _, num := range nums {
        sum += num
    }
    fmt.Println("sum:", sum)

::: {.en} range on arrays and slices provides both the index and value for each entry. Above we didn’t need the index, so we ignored it with the blank identifier _. Sometimes we actually want the indexes though. :::

::: {.zh}

对数组和切片使用 range 会返回每个条目的索引和值。上面我们不需要使用索引，所以我们用空白标识符 _ 忽略它。有时我们实际上需要索引。

:::

    for i, num := range nums {
        if num == 3 {
            fmt.Println("index:", i)
        }
    }

::: {.en} range on map iterates over key/value pairs. :::

::: {.zh}

range 在 map 中迭代键/值对。

:::

    kvs := map[string]string{"a": "apple", "b": "banana"}
    for k, v := range kvs {
        fmt.Printf("%s -> %sn", k, v)
    }

::: {.en} range can also iterate over just the keys of a map. :::

::: {.zh}

range 也可以仅遍历 map 的键。

:::

    for k := range kvs {
        fmt.Println("key:", k)
    }

::: {.en} range on strings iterates over Unicode code points. The first value is the starting byte index of the rune and the second the rune itself. :::

::: {.zh}

range 在字符串中遍历 Unicode 码点（code points）。第一个值是字符的起始字节位置，第二个值是字符本身。

:::

    for i, c := range "go" {
        fmt.Println(i, c)
    }
}

$ go run range.go
sum: 9
index: 1
a -> apple
b -> banana
key: a
key: b
0 103
1 111