In a Go slice, why does s[lo:hi] end at element hi-1?

Question

According to the Tour of Go, in a Go slice s, the expression s[lo:hi] evaluates to a slice of the elements from lo through hi-1<

Answer 1

The Go Programming Language Specification

Slice types

Slice expressions

For a string, array, pointer to array, or slice a, the primary expression

a[low : high]

constructs a substring or slice. The indices low and high select which elements of operand a appear in the result. The result has indices starting at 0 and length equal to high - low.

For convenience, any of the indices may be omitted. A missing low index defaults to zero; a missing high index defaults to the length of the sliced operand

For arrays or strings, the indices are in range if 0 <= low <= high <= len(a), otherwise they are out of range. For slices, the upper index bound is the slice capacity cap(a) rather than the length. A constant index must be non-negative and representable by a value of type int; for arrays or constant strings, constant indices must also be in range. If both indices are constant, they must satisfy low <= high. If the indices are out of range at run time, a run-time panic occurs.

For q := p[m:n], q is a slice of p starting at index m for a length of n-m elements.