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container/list: added MoveBefore and MoveAfter
Fixes #4940. R=golang-dev, bradfitz, gri CC=golang-dev https://golang.org/cl/12021044
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@ -179,6 +179,24 @@ func (l *List) MoveToBack(e *Element) {
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l.insert(l.remove(e), l.root.prev)
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}
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// MoveBefore moves element e to its new position before mark.
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// If e is not an element of l, or e == mark, the list is not modified.
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func (l *List) MoveBefore(e, mark *Element) {
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if e.list != l || e == mark {
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return
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}
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l.insert(l.remove(e), mark.prev)
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}
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// MoveAfter moves element e to its new position after mark.
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// If e is not an element of l, or e == mark, the list is not modified.
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func (l *List) MoveAfter(e, mark *Element) {
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if e.list != l || e == mark {
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return
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}
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l.insert(l.remove(e), mark)
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}
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// PushBackList inserts a copy of an other list at the back of list l.
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// The lists l and other may be the same.
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func (l *List) PushBackList(other *List) {
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@ -233,3 +233,37 @@ func TestIssue4103(t *testing.T) {
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t.Errorf("l1.Len() = %d, want 3", n)
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}
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}
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func TestMove(t *testing.T) {
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l := New()
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e1 := l.PushBack(1)
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e2 := l.PushBack(2)
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e3 := l.PushBack(3)
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e4 := l.PushBack(4)
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l.MoveAfter(e3, e3)
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checkListPointers(t, l, []*Element{e1, e2, e3, e4})
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l.MoveBefore(e2, e2)
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checkListPointers(t, l, []*Element{e1, e2, e3, e4})
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l.MoveAfter(e3, e2)
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checkListPointers(t, l, []*Element{e1, e2, e3, e4})
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l.MoveBefore(e2, e3)
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checkListPointers(t, l, []*Element{e1, e2, e3, e4})
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l.MoveBefore(e2, e4)
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checkListPointers(t, l, []*Element{e1, e3, e2, e4})
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e1, e2, e3, e4 = e1, e3, e2, e4
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l.MoveBefore(e4, e1)
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checkListPointers(t, l, []*Element{e4, e1, e2, e3})
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e1, e2, e3, e4 = e4, e1, e2, e3
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l.MoveAfter(e4, e1)
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checkListPointers(t, l, []*Element{e1, e4, e2, e3})
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e1, e2, e3, e4 = e1, e4, e2, e3
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l.MoveAfter(e2, e3)
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checkListPointers(t, l, []*Element{e1, e3, e2, e4})
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e1, e2, e3, e4 = e1, e3, e2, e4
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}
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