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slices: clarify MinFunc/MaxFunc result for equal elements
They should return the first of equal elements. No such clarification is required for Min/Max as for them equal elements are indistinguishable. For #60091 Change-Id: Iad58115d482add852c811e993131702b5b3bec5e Reviewed-on: https://go-review.googlesource.com/c/go/+/505796 Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Eli Bendersky <eliben@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Auto-Submit: Ian Lance Taylor <iant@google.com>
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@ -70,7 +70,8 @@ func Min[S ~[]E, E cmp.Ordered](x S) E {
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}
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// MinFunc returns the minimal value in x, using cmp to compare elements.
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// It panics if x is empty.
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// It panics if x is empty. If there is more than one minimal element
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// according to the cmp function, MinFunc returns the first one.
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func MinFunc[S ~[]E, E any](x S, cmp func(a, b E) int) E {
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if len(x) < 1 {
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panic("slices.MinFunc: empty list")
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@ -99,7 +100,8 @@ func Max[S ~[]E, E cmp.Ordered](x S) E {
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}
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// MaxFunc returns the maximal value in x, using cmp to compare elements.
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// It panics if x is empty.
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// It panics if x is empty. If there is more than one maximal element
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// according to the cmp function, MaxFunc returns the first one.
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func MaxFunc[S ~[]E, E any](x S, cmp func(a, b E) int) E {
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if len(x) < 1 {
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panic("slices.MaxFunc: empty list")
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@ -173,6 +173,15 @@ func TestStability(t *testing.T) {
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}
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}
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type S struct {
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a int
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b string
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}
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func cmpS(s1, s2 S) int {
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return cmp.Compare(s1.a, s2.a)
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}
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func TestMinMax(t *testing.T) {
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intCmp := func(a, b int) int { return a - b }
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@ -214,6 +223,25 @@ func TestMinMax(t *testing.T) {
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}
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})
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}
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svals := []S{
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{1, "a"},
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{2, "a"},
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{1, "b"},
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{2, "b"},
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}
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gotMin := MinFunc(svals, cmpS)
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wantMin := S{1, "a"}
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if gotMin != wantMin {
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t.Errorf("MinFunc(%v) = %v, want %v", svals, gotMin, wantMin)
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}
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gotMax := MaxFunc(svals, cmpS)
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wantMax := S{2, "a"}
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if gotMax != wantMax {
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t.Errorf("MaxFunc(%v) = %v, want %v", svals, gotMax, wantMax)
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}
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}
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func TestMinMaxNaNs(t *testing.T) {
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