Why Does `copy()` Fail to Duplicate Empty Slices in Go?

Understanding Why copy() Fails to Duplicate Empty Slices

In Go, the copy() function is intended for copying elements between two slices, allowing for potential overlap in the process. However, when attempting to copy an empty slice, unexpected behavior can arise.

The Root of the Issue:

The documentation states that copy() copies elements from a source slice into a destination slice, returning the number of elements copied. Crucially, this number is determined by the minimum length of the source and destination slices, as specified in the Go Language Specification.

Empty Destination Slice Problem:

When the destination slice is empty (i.e., len(dst) == 0), the minimum length becomes zero, resulting in no elements being copied. This is why in your example, copy() failed to populate your tmp slice.

Solution:

To circumvent this issue and successfully copy an empty slice, you must first initialize the destination slice with sufficient capacity. This can be achieved using make([]int, len(arr)).

Updated Documentation:

The documentation for copy() has been updated to explicitly state that the minimum of the source and destination slice lengths is copied. This clarification addresses the discrepancy encountered when attempting to duplicate empty slices.

The above is the detailed content of Why Does `copy()` Fail to Duplicate Empty Slices in Go?. For more information, please follow other related articles on the PHP Chinese website!