Home >Backend Development >Golang >Why Does Go's `s[lo:hi]` Slice Exclude the Element at Index `hi`?
The Go slice expression s[lo:hi] creates a slice containing elements from index lo to index hi-1, inclusive. This behavior is explained by several design principles:
In Go, slices are implemented as pointers to the underlying array. Using 0-indexed arrays and inclusive-exclusive slicing allows for straightforward pointer arithmetic. The element at index i in the slice is simply the element pointed to by the slice's pointer plus i.
The length of a Go slice is also the position at which to slice it. This means that arr[0:len(arr)] returns arr itself. This property is convenient for extracting data from a slice after a read or write operation.
Inclusive-exclusive slicing ensures that contiguous sub-slices of an array do not overlap. For example, if arr = [1, 2, 3, 4], then arr[0:2] = [1, 2], arr[2:4] = [3, 4], and arr[0:4] = arr. This property simplifies operations that require partitioning or manipulation of sub-slices.
Consider the following Go code:
func consecutiveSlices(ints []int) [][]int { ret := make([][]int, 0) i, j := 0, 1 for j < len(ints) { if ints[j] != ints[j-1] + 1 { ret = append(ret, ints[i:j]) i = j } } ret = append(ret, ints[i:j]) return ret }
This function splits a slice of integers into consecutive sub-slices based on the difference between each element and its predecessor. The inclusive-exclusive slicing technique allows for a simpler and more efficient implementation compared to using inclusive-inclusive slicing.
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