| // Copyright 2017, 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.md file. |
| |
| package cmp_test |
| |
| import ( |
| "fmt" |
| "math" |
| "reflect" |
| "sort" |
| "strings" |
| |
| "github.com/google/go-cmp/cmp" |
| ) |
| |
| // Approximate equality for floats can be handled by defining a custom |
| // comparer on floats that determines two values to be equal if they are within |
| // some range of each other. |
| func ExampleOption_approximateFloats() { |
| // This Comparer only operates on float64. |
| // To handle float32s, either define a similar function for that type |
| // or use a Transformer to convert float32s into float64s. |
| opt := cmp.Comparer(func(x, y float64) bool { |
| delta := math.Abs(x - y) |
| mean := math.Abs(x+y) / 2.0 |
| return delta/mean < 0.00001 |
| }) |
| |
| x := []float64{1.0, 1.1, 1.2, math.Pi} |
| y := []float64{1.0, 1.1, 1.2, 3.14159265359} // Accurate enough to Pi |
| z := []float64{1.0, 1.1, 1.2, 3.1415} // Diverges too far from Pi |
| |
| fmt.Println(cmp.Equal(x, y, opt)) |
| fmt.Println(cmp.Equal(y, z, opt)) |
| fmt.Println(cmp.Equal(z, x, opt)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |
| |
| // Normal floating-point arithmetic defines == to be false when comparing |
| // NaN with itself. In certain cases, this is not the desired property. |
| func ExampleOption_equalNaNs() { |
| // This Comparer only operates on float64. |
| // To handle float32s, either define a similar function for that type |
| // or use a Transformer to convert float32s into float64s. |
| opt := cmp.Comparer(func(x, y float64) bool { |
| return (math.IsNaN(x) && math.IsNaN(y)) || x == y |
| }) |
| |
| x := []float64{1.0, math.NaN(), math.E, -0.0, +0.0} |
| y := []float64{1.0, math.NaN(), math.E, -0.0, +0.0} |
| z := []float64{1.0, math.NaN(), math.Pi, -0.0, +0.0} // Pi constant instead of E |
| |
| fmt.Println(cmp.Equal(x, y, opt)) |
| fmt.Println(cmp.Equal(y, z, opt)) |
| fmt.Println(cmp.Equal(z, x, opt)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |
| |
| // To have floating-point comparisons combine both properties of NaN being |
| // equal to itself and also approximate equality of values, filters are needed |
| // to restrict the scope of the comparison so that they are composable. |
| func ExampleOption_equalNaNsAndApproximateFloats() { |
| alwaysEqual := cmp.Comparer(func(_, _ interface{}) bool { return true }) |
| |
| opts := cmp.Options{ |
| // This option declares that a float64 comparison is equal only if |
| // both inputs are NaN. |
| cmp.FilterValues(func(x, y float64) bool { |
| return math.IsNaN(x) && math.IsNaN(y) |
| }, alwaysEqual), |
| |
| // This option declares approximate equality on float64s only if |
| // both inputs are not NaN. |
| cmp.FilterValues(func(x, y float64) bool { |
| return !math.IsNaN(x) && !math.IsNaN(y) |
| }, cmp.Comparer(func(x, y float64) bool { |
| delta := math.Abs(x - y) |
| mean := math.Abs(x+y) / 2.0 |
| return delta/mean < 0.00001 |
| })), |
| } |
| |
| x := []float64{math.NaN(), 1.0, 1.1, 1.2, math.Pi} |
| y := []float64{math.NaN(), 1.0, 1.1, 1.2, 3.14159265359} // Accurate enough to Pi |
| z := []float64{math.NaN(), 1.0, 1.1, 1.2, 3.1415} // Diverges too far from Pi |
| |
| fmt.Println(cmp.Equal(x, y, opts)) |
| fmt.Println(cmp.Equal(y, z, opts)) |
| fmt.Println(cmp.Equal(z, x, opts)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |
| |
| // Sometimes, an empty map or slice is considered equal to an allocated one |
| // of zero length. |
| func ExampleOption_equalEmpty() { |
| alwaysEqual := cmp.Comparer(func(_, _ interface{}) bool { return true }) |
| |
| // This option handles slices and maps of any type. |
| opt := cmp.FilterValues(func(x, y interface{}) bool { |
| vx, vy := reflect.ValueOf(x), reflect.ValueOf(y) |
| return (vx.IsValid() && vy.IsValid() && vx.Type() == vy.Type()) && |
| (vx.Kind() == reflect.Slice || vx.Kind() == reflect.Map) && |
| (vx.Len() == 0 && vy.Len() == 0) |
| }, alwaysEqual) |
| |
| type S struct { |
| A []int |
| B map[string]bool |
| } |
| x := S{nil, make(map[string]bool, 100)} |
| y := S{make([]int, 0, 200), nil} |
| z := S{[]int{0}, nil} // []int has a single element (i.e., not empty) |
| |
| fmt.Println(cmp.Equal(x, y, opt)) |
| fmt.Println(cmp.Equal(y, z, opt)) |
| fmt.Println(cmp.Equal(z, x, opt)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |
| |
| // Two slices may be considered equal if they have the same elements, |
| // regardless of the order that they appear in. Transformations can be used |
| // to sort the slice. |
| func ExampleOption_sortedSlice() { |
| // This Transformer sorts a []int. |
| // Since the transformer transforms []int into []int, there is problem where |
| // this is recursively applied forever. To prevent this, use a FilterValues |
| // to first check for the condition upon which the transformer ought to apply. |
| trans := cmp.FilterValues(func(x, y []int) bool { |
| return !sort.IntsAreSorted(x) || !sort.IntsAreSorted(y) |
| }, cmp.Transformer("Sort", func(in []int) []int { |
| out := append([]int(nil), in...) // Copy input to avoid mutating it |
| sort.Ints(out) |
| return out |
| })) |
| |
| x := struct{ Ints []int }{[]int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}} |
| y := struct{ Ints []int }{[]int{2, 8, 0, 9, 6, 1, 4, 7, 3, 5}} |
| z := struct{ Ints []int }{[]int{0, 0, 1, 2, 3, 4, 5, 6, 7, 8}} |
| |
| fmt.Println(cmp.Equal(x, y, trans)) |
| fmt.Println(cmp.Equal(y, z, trans)) |
| fmt.Println(cmp.Equal(z, x, trans)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |
| |
| type otherString string |
| |
| func (x otherString) Equal(y otherString) bool { |
| return strings.ToLower(string(x)) == strings.ToLower(string(y)) |
| } |
| |
| // If the Equal method defined on a type is not suitable, the type can be be |
| // dynamically transformed to be stripped of the Equal method (or any method |
| // for that matter). |
| func ExampleOption_avoidEqualMethod() { |
| // Suppose otherString.Equal performs a case-insensitive equality, |
| // which is too loose for our needs. |
| // We can avoid the methods of otherString by declaring a new type. |
| type myString otherString |
| |
| // This transformer converts otherString to myString, allowing Equal to use |
| // other Options to determine equality. |
| trans := cmp.Transformer("", func(in otherString) myString { |
| return myString(in) |
| }) |
| |
| x := []otherString{"foo", "bar", "baz"} |
| y := []otherString{"fOO", "bAr", "Baz"} // Same as before, but with different case |
| |
| fmt.Println(cmp.Equal(x, y)) // Equal because of case-insensitivity |
| fmt.Println(cmp.Equal(x, y, trans)) // Not equal because of more exact equality |
| |
| // Output: |
| // true |
| // false |
| } |
| |
| func roundF64(z float64) float64 { |
| if z < 0 { |
| return math.Ceil(z - 0.5) |
| } |
| return math.Floor(z + 0.5) |
| } |
| |
| // The complex numbers complex64 and complex128 can really just be decomposed |
| // into a pair of float32 or float64 values. It would be convenient to be able |
| // define only a single comparator on float64 and have float32, complex64, and |
| // complex128 all be able to use that comparator. Transformations can be used |
| // to handle this. |
| func ExampleOption_transformComplex() { |
| opts := []cmp.Option{ |
| // This transformer decomposes complex128 into a pair of float64s. |
| cmp.Transformer("T1", func(in complex128) (out struct{ Real, Imag float64 }) { |
| out.Real, out.Imag = real(in), imag(in) |
| return out |
| }), |
| // This transformer converts complex64 to complex128 to allow the |
| // above transform to take effect. |
| cmp.Transformer("T2", func(in complex64) complex128 { |
| return complex128(in) |
| }), |
| // This transformer converts float32 to float64. |
| cmp.Transformer("T3", func(in float32) float64 { |
| return float64(in) |
| }), |
| // This equality function compares float64s as rounded integers. |
| cmp.Comparer(func(x, y float64) bool { |
| return roundF64(x) == roundF64(y) |
| }), |
| } |
| |
| x := []interface{}{ |
| complex128(3.0), complex64(5.1 + 2.9i), float32(-1.2), float64(12.3), |
| } |
| y := []interface{}{ |
| complex128(3.1), complex64(4.9 + 3.1i), float32(-1.3), float64(11.7), |
| } |
| z := []interface{}{ |
| complex128(3.8), complex64(4.9 + 3.1i), float32(-1.3), float64(11.7), |
| } |
| |
| fmt.Println(cmp.Equal(x, y, opts...)) |
| fmt.Println(cmp.Equal(y, z, opts...)) |
| fmt.Println(cmp.Equal(z, x, opts...)) |
| |
| // Output: |
| // true |
| // false |
| // false |
| } |