Why Does Go's Slice Indexing `s[lo:hi]` Exclude the `hi`-th Element?

Understanding Slice Indexing in Go: Why s[lo:hi] Ends at Element hi-1

In Go, slices represent sequences of elements. When slicing a slice, the expression s[lo:hi] returns a new slice that contains elements from index lo (inclusive) to hi (exclusive).

Rationale for the Inclusive-Exclusive Slicing

The choice of using inclusive-exclusive slicing (where hi-1 is used as the upper bound) instead of inclusive-inclusive slicing (where hi is used as the upper bound) is based on several advantages:

• Pointer Arithmetic Simplicity: Go slices are stored as pointers, and the inclusive-exclusive method allows for simple pointer arithmetic. Each element in a slice is located at the memory address of the slice pointer plus its index, making it straightforward for pointer operations.
• Slice Length Utility: The length of a slice is also the same as the index at which it can be sliced to obtain the original slice. For instance, s[0:len(s)] provides the original slice s. This simplifies operations involving slice manipulation.
• Non-Overlapping Indices: Inclusive-exclusive slicing ensures that the indices of subsequent slices do not overlap. If we have slices s[lo1:hi1], s[hi1:hi2], s[hi2:hi3], and so on, these slices together cover the entire original slice s.
• Simplified Splitting Algorithm: This slicing method simplifies algorithms that split arrays based on non-consecutive integers. In contrast, inclusive-inclusive slicing requires more complex logic to achieve the same result.

Example:

Consider the following slice:

p := []int{0, 10, 20, 30, 40, 50}

• p[0:3] would return [0, 10, 20], excluding element 30.
• p[3:6] would return [30, 40, 50], including element 30.
• p[0:len(p)] would return the original slice p.

Conclusion:

The inclusive-exclusive slicing method in Go provides simplicity in pointer arithmetic, convenient slice manipulation, and facilitates the creation of efficient algorithms for slice operations.

The above is the detailed content of Why Does Go's Slice Indexing `s[lo:hi]` Exclude the `hi`-th Element?. For more information, please follow other related articles on the PHP Chinese website!