Why Does Go's Slice Syntax Exclude the Upper Bound?

Why Does Slice Syntax in Go Exclude the High Boundary (hi)?

The Go slice syntax s[lo:hi] specifies a range of elements from index lo (inclusive) to hi-1 (exclusive). This differs from the intuitive expectation that hi would be included in the range.

Design Rationale

The choice of exclusive slicing is a matter of convention and offers several advantages:

• Pointer Arithmetic Simplicity: In Go, slices are essentially pointers with an associated length. With 0-indexed arrays and exclusive slicing, the address of element i is simply the pointer value plus i.
• Convenient Array Length: The length of a slice is also its "split point." This means arr[0:len(arr)] is equivalent to arr, making it convenient for operations such as splitting an array into segments.
• Non-Overlapping Indices: Exclusive slicing ensures that consecutive slices fully cover the original array. This simplifies operations like splitting an array based on non-consecutive integers.

In contrast, inclusive slicing - where [lo:hi] includes both lo and hi - would result in overlapping slices and complicate certain operations.

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