whatcanGOwrong
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package maps defines various functions useful with maps of any type.
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package maps
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// Keys returns the keys of the map m.
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// The keys will be in an indeterminate order.
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func Keys[M ~map[K]V, K comparable, V any](m M) []K {
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r := make([]K, 0, len(m))
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for k := range m {
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r = append(r, k)
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}
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return r
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}
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// Values returns the values of the map m.
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// The values will be in an indeterminate order.
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func Values[M ~map[K]V, K comparable, V any](m M) []V {
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r := make([]V, 0, len(m))
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for _, v := range m {
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r = append(r, v)
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}
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return r
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}
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// Equal reports whether two maps contain the same key/value pairs.
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// Values are compared using ==.
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func Equal[M1, M2 ~map[K]V, K, V comparable](m1 M1, m2 M2) bool {
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if len(m1) != len(m2) {
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return false
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}
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for k, v1 := range m1 {
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if v2, ok := m2[k]; !ok || v1 != v2 {
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return false
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}
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}
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return true
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}
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// EqualFunc is like Equal, but compares values using eq.
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// Keys are still compared with ==.
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func EqualFunc[M1 ~map[K]V1, M2 ~map[K]V2, K comparable, V1, V2 any](m1 M1, m2 M2, eq func(V1, V2) bool) bool {
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if len(m1) != len(m2) {
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return false
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}
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for k, v1 := range m1 {
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if v2, ok := m2[k]; !ok || !eq(v1, v2) {
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return false
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}
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}
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return true
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}
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// Clear removes all entries from m, leaving it empty.
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func Clear[M ~map[K]V, K comparable, V any](m M) {
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for k := range m {
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delete(m, k)
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}
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}
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// Clone returns a copy of m. This is a shallow clone:
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// the new keys and values are set using ordinary assignment.
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func Clone[M ~map[K]V, K comparable, V any](m M) M {
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// Preserve nil in case it matters.
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if m == nil {
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return nil
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}
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r := make(M, len(m))
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for k, v := range m {
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r[k] = v
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}
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return r
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}
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// Copy copies all key/value pairs in src adding them to dst.
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// When a key in src is already present in dst,
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// the value in dst will be overwritten by the value associated
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// with the key in src.
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func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2) {
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for k, v := range src {
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dst[k] = v
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}
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}
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// DeleteFunc deletes any key/value pairs from m for which del returns true.
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func DeleteFunc[M ~map[K]V, K comparable, V any](m M, del func(K, V) bool) {
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for k, v := range m {
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if del(k, v) {
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delete(m, k)
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}
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}
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}
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@@ -0,0 +1,181 @@
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package maps
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import (
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"math"
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"sort"
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"strconv"
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"testing"
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"golang.org/x/exp/slices"
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)
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var m1 = map[int]int{1: 2, 2: 4, 4: 8, 8: 16}
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var m2 = map[int]string{1: "2", 2: "4", 4: "8", 8: "16"}
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func TestKeys(t *testing.T) {
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want := []int{1, 2, 4, 8}
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got1 := Keys(m1)
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sort.Ints(got1)
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if !slices.Equal(got1, want) {
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t.Errorf("Keys(%v) = %v, want %v", m1, got1, want)
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}
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got2 := Keys(m2)
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sort.Ints(got2)
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if !slices.Equal(got2, want) {
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t.Errorf("Keys(%v) = %v, want %v", m2, got2, want)
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}
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}
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func TestValues(t *testing.T) {
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got1 := Values(m1)
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want1 := []int{2, 4, 8, 16}
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sort.Ints(got1)
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if !slices.Equal(got1, want1) {
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t.Errorf("Values(%v) = %v, want %v", m1, got1, want1)
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}
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got2 := Values(m2)
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want2 := []string{"16", "2", "4", "8"}
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sort.Strings(got2)
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if !slices.Equal(got2, want2) {
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t.Errorf("Values(%v) = %v, want %v", m2, got2, want2)
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}
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}
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func TestEqual(t *testing.T) {
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if !Equal(m1, m1) {
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t.Errorf("Equal(%v, %v) = false, want true", m1, m1)
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}
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if Equal(m1, (map[int]int)(nil)) {
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t.Errorf("Equal(%v, nil) = true, want false", m1)
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}
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if Equal((map[int]int)(nil), m1) {
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t.Errorf("Equal(nil, %v) = true, want false", m1)
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}
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if !Equal[map[int]int, map[int]int](nil, nil) {
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t.Error("Equal(nil, nil) = false, want true")
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}
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if ms := map[int]int{1: 2}; Equal(m1, ms) {
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t.Errorf("Equal(%v, %v) = true, want false", m1, ms)
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}
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// Comparing NaN for equality is expected to fail.
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mf := map[int]float64{1: 0, 2: math.NaN()}
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if Equal(mf, mf) {
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t.Errorf("Equal(%v, %v) = true, want false", mf, mf)
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}
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}
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// equal is simply ==.
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func equal[T comparable](v1, v2 T) bool {
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return v1 == v2
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}
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// equalNaN is like == except that all NaNs are equal.
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func equalNaN[T comparable](v1, v2 T) bool {
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isNaN := func(f T) bool { return f != f }
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return v1 == v2 || (isNaN(v1) && isNaN(v2))
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}
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// equalStr compares ints and strings.
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func equalIntStr(v1 int, v2 string) bool {
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return strconv.Itoa(v1) == v2
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}
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func TestEqualFunc(t *testing.T) {
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if !EqualFunc(m1, m1, equal[int]) {
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t.Errorf("EqualFunc(%v, %v, equal) = false, want true", m1, m1)
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}
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if EqualFunc(m1, (map[int]int)(nil), equal[int]) {
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t.Errorf("EqualFunc(%v, nil, equal) = true, want false", m1)
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}
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if EqualFunc((map[int]int)(nil), m1, equal[int]) {
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t.Errorf("EqualFunc(nil, %v, equal) = true, want false", m1)
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}
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if !EqualFunc[map[int]int, map[int]int](nil, nil, equal[int]) {
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t.Error("EqualFunc(nil, nil, equal) = false, want true")
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}
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if ms := map[int]int{1: 2}; EqualFunc(m1, ms, equal[int]) {
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t.Errorf("EqualFunc(%v, %v, equal) = true, want false", m1, ms)
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}
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// Comparing NaN for equality is expected to fail.
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mf := map[int]float64{1: 0, 2: math.NaN()}
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if EqualFunc(mf, mf, equal[float64]) {
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t.Errorf("EqualFunc(%v, %v, equal) = true, want false", mf, mf)
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}
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// But it should succeed using equalNaN.
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if !EqualFunc(mf, mf, equalNaN[float64]) {
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t.Errorf("EqualFunc(%v, %v, equalNaN) = false, want true", mf, mf)
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}
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if !EqualFunc(m1, m2, equalIntStr) {
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t.Errorf("EqualFunc(%v, %v, equalIntStr) = false, want true", m1, m2)
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}
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}
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func TestClear(t *testing.T) {
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ml := map[int]int{1: 1, 2: 2, 3: 3}
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Clear(ml)
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if got := len(ml); got != 0 {
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t.Errorf("len(%v) = %d after Clear, want 0", ml, got)
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}
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if !Equal(ml, (map[int]int)(nil)) {
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t.Errorf("Equal(%v, nil) = false, want true", ml)
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}
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}
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func TestClone(t *testing.T) {
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mc := Clone(m1)
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if !Equal(mc, m1) {
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t.Errorf("Clone(%v) = %v, want %v", m1, mc, m1)
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}
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mc[16] = 32
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if Equal(mc, m1) {
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t.Errorf("Equal(%v, %v) = true, want false", mc, m1)
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}
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}
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func TestCloneNil(t *testing.T) {
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var m1 map[string]int
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mc := Clone(m1)
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if mc != nil {
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t.Errorf("Clone(%v) = %v, want %v", m1, mc, m1)
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}
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}
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func TestCopy(t *testing.T) {
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mc := Clone(m1)
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Copy(mc, mc)
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if !Equal(mc, m1) {
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t.Errorf("Copy(%v, %v) = %v, want %v", m1, m1, mc, m1)
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}
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Copy(mc, map[int]int{16: 32})
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want := map[int]int{1: 2, 2: 4, 4: 8, 8: 16, 16: 32}
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if !Equal(mc, want) {
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t.Errorf("Copy result = %v, want %v", mc, want)
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}
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type M1 map[int]bool
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type M2 map[int]bool
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Copy(make(M1), make(M2))
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}
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func TestDeleteFunc(t *testing.T) {
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mc := Clone(m1)
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DeleteFunc(mc, func(int, int) bool { return false })
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if !Equal(mc, m1) {
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t.Errorf("DeleteFunc(%v, true) = %v, want %v", m1, mc, m1)
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}
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DeleteFunc(mc, func(k, v int) bool { return k > 3 })
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want := map[int]int{1: 2, 2: 4}
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if !Equal(mc, want) {
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t.Errorf("DeleteFunc result = %v, want %v", mc, want)
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}
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}
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