encoding/xml: move Unmarshal example to function

This also fixes MarshalIndent's example after the
recent formatting convention changes.

Fixes #2831.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5671062

src/pkg/encoding/xml/example_test.go

@@ -10,15 +10,6 @@ import (
 	"os"
 )
 
-//	<person id="13">
-//		<name>
-//			<first>John</first>
-//			<last>Doe</last>
-//		</name>
-//		<age>42</age>
-//		<Married>false</Married>
-//		<!-- Need more fields. -->
-//	</person>
 func ExampleMarshalIndent() {
 	type Person struct {
 		XMLName   xml.Name `xml:"person"`
@@ -34,10 +25,72 @@ func ExampleMarshalIndent() {
 	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
 	v.Comment = " Need more fields. "
 
-	output, err := xml.MarshalIndent(v, "\t", "\t")
+	output, err := xml.MarshalIndent(v, "  ", "    ")
 	if err != nil {
 		fmt.Printf("error: %v\n", err)
 	}
 
 	os.Stdout.Write(output)
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <!-- Need more fields. -->
+	//   </person>
+}
+
+// This example demonstrates unmarshaling an XML excerpt into a value with
+// some preset fields. Note that the Phone field isn't modified and that
+// the XML <address> element is ignored. Also, the Groups field is assigned
+// considering the element path provided in its tag.
+func ExampleUnmarshal() {
+	type Email struct {
+		Where string `xml:"where,attr"`
+		Addr  string
+	}
+	type Result struct {
+		XMLName xml.Name `xml:"Person"`
+		Name    string   `xml:"FullName"`
+		Phone   string
+		Email   []Email
+		Groups  []string `xml:"Group>Value"`
+	}
+	p := Result{Name: "none", Phone: "none"}
+
+	data := `
+		<Person>
+			<FullName>Grace R. Emlin</FullName>
+			<Email where="home">
+				<Addr>gre@example.com</Addr>
+			</Email>
+			<Email where='work'>
+				<Addr>gre@work.com</Addr>
+			</Email>
+			<Group>
+				<Value>Friends</Value>
+				<Value>Squash</Value>
+			</Group>
+			<Address>123 Main Street</Address>
+		</Person>
+	`
+	err := xml.Unmarshal([]byte(data), &p)
+	if err != nil {
+		fmt.Printf("error: %v", err)
+		return
+	}
+	fmt.Printf("XMLName: %#v\n", p.XMLName)
+	fmt.Printf("Name: %q\n", p.Name)
+	fmt.Printf("Phone: %q\n", p.Phone)
+	fmt.Printf("Email: %v\n", p.Email)
+	fmt.Printf("Groups: %v\n", p.Groups)
+	// Output:
+	// XMLName: xml.Name{Space:"", Local:"Person"}
+	// Name: "Grace R. Emlin"
+	// Phone: "none"
+	// Email: [{home gre@example.com} {work gre@work.com}]
+	// Groups: [Friends Squash]
 }

src/pkg/encoding/xml/read.go

@@ -25,58 +25,6 @@ import (
 // slice, or string. Well-formed data that does not fit into v is
 // discarded.
 //
-// For example, given these definitions:
-//
-//	type Email struct {
-//		Where string `xml:",attr"`
-//		Addr  string
-//	}
-//
-//	type Result struct {
-//		XMLName xml.Name `xml:"result"`
-//		Name	string
-//		Phone	string
-//		Email	[]Email
-//		Groups  []string `xml:"group>value"`
-//	}
-//
-//	result := Result{Name: "name", Phone: "phone", Email: nil}
-//
-// unmarshalling the XML input
-//
-//	<result>
-//		<email where="home">
-//			<addr>gre@example.com</addr>
-//		</email>
-//		<email where='work'>
-//			<addr>gre@work.com</addr>
-//		</email>
-//		<name>Grace R. Emlin</name>
-// 		<group>
-// 			<value>Friends</value>
-// 			<value>Squash</value>
-// 		</group>
-//		<address>123 Main Street</address>
-//	</result>
-//
-// via Unmarshal(data, &result) is equivalent to assigning
-//
-//	r = Result{
-//		xml.Name{Local: "result"},
-//		"Grace R. Emlin", // name
-//		"phone",	  // no phone given
-//		[]Email{
-//			Email{"home", "gre@example.com"},
-//			Email{"work", "gre@work.com"},
-//		},
-//		[]string{"Friends", "Squash"},
-//	}
-//
-// Note that the field r.Phone has not been modified and
-// that the XML <address> element was discarded. Also, the field
-// Groups was assigned considering the element path provided in the
-// field tag.
-//
 // Because Unmarshal uses the reflect package, it can only assign
 // to exported (upper case) fields.  Unmarshal uses a case-sensitive
 // comparison to match XML element names to tag values and struct