Added and corrected comments

link.go

@@ -17,6 +17,7 @@ type Link struct {
 	Length   uint        `xml:"length,attr,omitempty"`
 }
 
+// NewLink creates a new Link. It returns a *Link and an error.
 func NewLink(href string) (*Link, error) {
 	content, err := NewContent(InlineText, "", "")
 	if err != nil {
@@ -26,6 +27,8 @@ func NewLink(href string) (*Link, error) {
 	return &Link{Href: IRI(href), Content: content}, nil
 }
 
+// Check checks the Link for incompatibilities with RFC4287. It returns an
+// error.
 func (l *Link) Check() error {
 	if l.Href == "" {
 		return errors.New("href attribute of link empty")
@@ -58,6 +61,8 @@ func (l *Link) Check() error {
 	return nil
 }
 
+// hasAlternateDuplicateLinks checks whether multiple Links with Rel
+// "alternate" also have Type and HrefLang in common. It returns a bool.
 // atom:feed/entry elements MUST NOT contain more than one atom:link element
 // with a rel attribute value of "alternate" that has the same combination of
 // type and hreflang attribute values.
@@ -76,3 +81,15 @@ func hasAlternateDuplicateLinks(l []*Link) bool {
 
 	return false
 }
+
+// alternateRelExists checks whether multiple Links with Rel "alternate" exist.
+// It returns a bool.
+func alternateRelExists(l []*Link) bool {
+	for _, link := range l {
+		if link.Rel == "alternate" {
+			return true
+		}
+	}
+
+	return false
+}