| _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. | ||
package main |
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import "fmt" |
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func main() { |
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| Here we use `range` to sum the numbers in a slice. Arrays work like this too. | nums := []int{2, 3, 4} |
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sum := 0 |
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for _, num := range nums { |
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sum += num |
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} |
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fmt.Println("sum:", sum) |
sum: 9 |
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| `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. | for i, num := range nums { |
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if num == 3 { |
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fmt.Println("index:", i) |
index: 1 |
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} |
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} |
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| `range` on map iterates over key/value pairs. | kvs := map[string]string{"a": "apple", "b": "banana"} |
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for k, v := range kvs { |
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fmt.Printf("%s -> %s\n", k, v) |
a -> apple b -> banana |
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} |
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| `range` can also iterate over just the keys of a map. | for k := range kvs { |
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fmt.Println("key:", k) |
key: a key: b |
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} |
a -> apple |
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| `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. | for i, c := range "go" { |
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fmt.Println(i, c) |
0 103 1 111 |
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} |
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} |