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slices: add in-place Reverse function
Fixes #58565 Change-Id: I583f8380c12386178fb18e553322bbb019d9fae0 Reviewed-on: https://go-review.googlesource.com/c/go/+/468855 Run-TryBot: Alan Donovan <adonovan@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Shay Nehmad <dude500@gmail.com>
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api/next/58565.txt
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api/next/58565.txt
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@ -0,0 +1 @@
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pkg slices, func Reverse[$0 interface{}]([]$0) #58565
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@ -668,6 +668,16 @@ Do not send CLs removing the interior tags from such phrases.
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</dd>
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</dl><!-- spec -->
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<dl id="slices"><dt><a href="/pkg/slices/">slices</a></dt>
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<dd>
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<p><!-- https://go.dev/issue/45955 -->
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The new <a href="/pkg/slices/"><code>slices</code></a> package
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provides many common operations on slices, using generic
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functions that work with slices of any element type.
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</p>
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</dd>
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</dl>
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<dl id="sync"><dt><a href="/pkg/sync/">sync</a></dt>
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<dd>
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<p><!-- https://go.dev/issue/56102, CL 451356 -->
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@ -445,3 +445,10 @@ func startIdx[S ~[]E, E any](haystack, needle S) int {
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// TODO: what if the overlap is by a non-integral number of Es?
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panic("needle not found")
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}
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// Reverse reverses the elements of the slice in place.
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func Reverse[E any](s []E) {
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for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
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s[i], s[j] = s[j], s[i]
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}
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}
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@ -623,6 +623,34 @@ func TestClip(t *testing.T) {
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}
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}
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func TestReverse(t *testing.T) {
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even := []int{3, 1, 4, 1, 5, 9} // len = 6
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Reverse(even)
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if want := []int{9, 5, 1, 4, 1, 3}; !Equal(even, want) {
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t.Errorf("Reverse(even) = %v, want %v", even, want)
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}
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odd := []int{3, 1, 4, 1, 5, 9, 2} // len = 7
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Reverse(odd)
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if want := []int{2, 9, 5, 1, 4, 1, 3}; !Equal(odd, want) {
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t.Errorf("Reverse(odd) = %v, want %v", odd, want)
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}
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words := strings.Fields("one two three")
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Reverse(words)
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if want := strings.Fields("three two one"); !Equal(words, want) {
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t.Errorf("Reverse(words) = %v, want %v", words, want)
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}
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singleton := []string{"one"}
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Reverse(singleton)
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if want := []string{"one"}; !Equal(singleton, want) {
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t.Errorf("Reverse(singeleton) = %v, want %v", singleton, want)
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}
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Reverse[string](nil)
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}
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// naiveReplace is a baseline implementation to the Replace function.
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func naiveReplace[S ~[]E, E any](s S, i, j int, v ...E) S {
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s = Delete(s, i, j)
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