Go language slice: Why does it not report an error when single-element slice index 1 intercept?

Detailed explanation of Go language slice index: Why does a single-element slice intercept from index 1 without an error?

Slicing in Go is a powerful dynamic array structure that references part of the underlying array. However, for single-element slices, intercepting from index 1 does not throw an error, which is often confusing. This article will analyze the mechanism of Go language slices in depth and explain this phenomenon.

The following code example shows this feature:

 func main() {
    arr := []int{7}
    s := arr[1:]
    fmt.Println(s) // Output[]
}

In the code, arr is an integer slice containing a single element 7. arr[1:] attempts to intercept the slice from index 1. The program run result does not report an error, but outputs an empty slice [] .

This is not a bug in Go language, but a reflection of its slice indexing mechanism. The Go language slice uses a semi-open interval notation, [i:j] means starting from index i and ending from index j , but does not include index j .

Therefore, arr[1:] is equivalent to arr[1:len(arr)] . In this example, len(arr) is 1, so arr[1:1] means starting from index 1 to ending index 1 (not including index 1), and the result is naturally an empty slice.

To understand more clearly, let's look at a slice containing multiple elements:

 func main() {
    arr := []int{7, 2}
    s := arr[:2]
    fmt.Println(s) // Output [7 2]
}

arr[:2] means starting from index 0 to ending index 2 (excluding index 2), and contains all elements. This once again confirms the characteristics of the half-open interval of the Go language slice, and also explains why a single-element slice will not report an error when intercepting from index 1, but will return an empty slice. This operation is allowed, and it also makes creating empty slices more convenient.

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