maps: add examples for Clone,Copy and Equal

Change-Id: I72adaf48588e7d6cffbc0ee8005decda06808e84
Reviewed-on: https://go-review.googlesource.com/c/go/+/534055
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: shuang cui <imcusg@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

src/maps/example_test.go

@@ -10,6 +10,72 @@ import (
 	"strings"
 )
 
+func ExampleClone() {
+	m1 := map[string]int{
+		"key": 1,
+	}
+	m2 := maps.Clone(m1)
+	m2["key"] = 100
+	fmt.Println(m1["key"])
+	fmt.Println(m2["key"])
+
+	m3 := map[string][]int{
+		"key": {1, 2, 3},
+	}
+	m4 := maps.Clone(m3)
+	fmt.Println(m4["key"][0])
+	m4["key"][0] = 100
+	fmt.Println(m3["key"][0])
+	fmt.Println(m4["key"][0])
+
+	// Output:
+	// 1
+	// 100
+	// 1
+	// 100
+	// 100
+}
+
+func ExampleCopy() {
+	m1 := map[string]int{
+		"one": 1,
+		"two": 2,
+	}
+	m2 := map[string]int{
+		"one": 10,
+	}
+
+	maps.Copy(m2, m1)
+	fmt.Println("m2 is:", m2)
+
+	m2["one"] = 100
+	fmt.Println("m1 is:", m1)
+	fmt.Println("m2 is:", m2)
+
+	m3 := map[string][]int{
+		"one": {1, 2, 3},
+		"two": {4, 5, 6},
+	}
+	m4 := map[string][]int{
+		"one": {7, 8, 9},
+	}
+
+	maps.Copy(m4, m3)
+	fmt.Println("m4 is:", m4)
+
+	m4["one"][0] = 100
+	fmt.Println("m3 is:", m3)
+	fmt.Println("m4 is:", m4)
+
+	// Output:
+	// m2 is: map[one:1 two:2]
+	// m1 is: map[one:1 two:2]
+	// m2 is: map[one:100 two:2]
+	// m4 is: map[one:[1 2 3] two:[4 5 6]]
+	// m3 is: map[one:[100 2 3] two:[4 5 6]]
+	// m4 is: map[one:[100 2 3] two:[4 5 6]]
+}
+
 func ExampleDeleteFunc() {
 	m := map[string]int{
 		"one":   1,
@@ -25,6 +91,30 @@ func ExampleDeleteFunc() {
 	// map[four:4 two:2]
 }
 
+func ExampleEqual() {
+	m1 := map[int]string{
+		1:    "one",
+		10:   "Ten",
+		1000: "THOUSAND",
+	}
+	m2 := map[int]string{
+		1:    "one",
+		10:   "Ten",
+		1000: "THOUSAND",
+	}
+	m3 := map[int]string{
+		1:    "one",
+		10:   "ten",
+		1000: "thousand",
+	}
+
+	fmt.Println(maps.Equal(m1, m2))
+	fmt.Println(maps.Equal(m1, m3))
+	// Output:
+	// true
+	// false
+}
+
 func ExampleEqualFunc() {
 	m1 := map[int]string{
 		1:    "one",