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 // Copyright 2023 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package runtime_test import ( "math" "strings" "testing" "unsafe" ) var ( zero = math.Copysign(0, +1) negZero = math.Copysign(0, -1) inf = math.Inf(+1) negInf = math.Inf(-1) nan = math.NaN() ) var tests = []struct{ min, max float64 }{ {1, 2}, {-2, 1}, {negZero, zero}, {zero, inf}, {negInf, zero}, {negInf, inf}, {1, inf}, {negInf, 1}, } var all = []float64{1, 2, -1, -2, zero, negZero, inf, negInf, nan} func eq(x, y float64) bool { return x == y && math.Signbit(x) == math.Signbit(y) } func TestMinFloat(t *testing.T) { for _, tt := range tests { if z := min(tt.min, tt.max); !eq(z, tt.min) { t.Errorf("min(%v, %v) = %v, want %v", tt.min, tt.max, z, tt.min) } if z := min(tt.max, tt.min); !eq(z, tt.min) { t.Errorf("min(%v, %v) = %v, want %v", tt.max, tt.min, z, tt.min) } } for _, x := range all { if z := min(nan, x); !math.IsNaN(z) { t.Errorf("min(%v, %v) = %v, want %v", nan, x, z, nan) } if z := min(x, nan); !math.IsNaN(z) { t.Errorf("min(%v, %v) = %v, want %v", nan, x, z, nan) } } } func TestMaxFloat(t *testing.T) { for _, tt := range tests { if z := max(tt.min, tt.max); !eq(z, tt.max) { t.Errorf("max(%v, %v) = %v, want %v", tt.min, tt.max, z, tt.max) } if z := max(tt.max, tt.min); !eq(z, tt.max) { t.Errorf("max(%v, %v) = %v, want %v", tt.max, tt.min, z, tt.max) } } for _, x := range all { if z := max(nan, x); !math.IsNaN(z) { t.Errorf("max(%v, %v) = %v, want %v", nan, x, z, nan) } if z := max(x, nan); !math.IsNaN(z) { t.Errorf("max(%v, %v) = %v, want %v", nan, x, z, nan) } } } // testMinMax tests that min/max behave correctly on every pair of // values in vals. // // vals should be a sequence of values in strictly ascending order. func testMinMax[T int | uint8 | string](t *testing.T, vals ...T) { for i, x := range vals { for _, y := range vals[i+1:] { if !(x < y) { t.Fatalf("values out of order: !(%v < %v)", x, y) } if z := min(x, y); z != x { t.Errorf("min(%v, %v) = %v, want %v", x, y, z, x) } if z := min(y, x); z != x { t.Errorf("min(%v, %v) = %v, want %v", y, x, z, x) } if z := max(x, y); z != y { t.Errorf("max(%v, %v) = %v, want %v", x, y, z, y) } if z := max(y, x); z != y { t.Errorf("max(%v, %v) = %v, want %v", y, x, z, y) } } } } func TestMinMaxInt(t *testing.T) { testMinMax[int](t, -7, 0, 9) } func TestMinMaxUint8(t *testing.T) { testMinMax[uint8](t, 0, 1, 2, 4, 7) } func TestMinMaxString(t *testing.T) { testMinMax[string](t, "a", "b", "c") } // TestMinMaxStringTies ensures that min(a, b) returns a when a == b. func TestMinMaxStringTies(t *testing.T) { s := "xxx" x := strings.Split(s, "") test := func(i, j, k int) { if z := min(x[i], x[j], x[k]); unsafe.StringData(z) != unsafe.StringData(x[i]) { t.Errorf("min(x[%v], x[%v], x[%v]) = %p, want %p", i, j, k, unsafe.StringData(z), unsafe.StringData(x[i])) } if z := max(x[i], x[j], x[k]); unsafe.StringData(z) != unsafe.StringData(x[i]) { t.Errorf("max(x[%v], x[%v], x[%v]) = %p, want %p", i, j, k, unsafe.StringData(z), unsafe.StringData(x[i])) } } test(0, 1, 2) test(0, 2, 1) test(1, 0, 2) test(1, 2, 0) test(2, 0, 1) test(2, 1, 0) } func BenchmarkMinFloat(b *testing.B) { var m float64 = 0 for i := 0; i < b.N; i++ { for _, f := range all { m = min(m, f) } } } func BenchmarkMaxFloat(b *testing.B) { var m float64 = 0 for i := 0; i < b.N; i++ { for _, f := range all { m = max(m, f) } } }