diff --git a/proc/comment.go b/proc/comment.go
new file mode 100644
index 0000000..a7854c8
--- /dev/null
+++ b/proc/comment.go
@@ -0,0 +1,91 @@
+package proc
+
+import (
+	"strings"
+)
+
+// CommentLines comment the line like `// xxxx`
+type CommentLines []string
+
+func NewCommentLines(s string) CommentLines {
+	if !strings.HasPrefix(s, "//") {
+		s = "// " + strings.TrimSpace(s)
+	}
+	return strings.Split(strings.TrimSuffix(s, "\n"), "\n")
+}
+
+// Derives all match the derive and remaining comment lines.
+func (c CommentLines) Derives() ([]*Derive, CommentLines) {
+	remain := make(CommentLines, 0, len(c))
+	ret := make([]*Derive, 0, len(c))
+	for _, s := range c {
+		if m, err := Match(strings.TrimSpace(strings.TrimPrefix(s, "//"))); err != nil {
+			remain = append(remain, s)
+		} else {
+			ret = append(ret, m)
+		}
+	}
+	return ret, remain
+}
+
+// Annotations find `identity` match the annotation and remaining comment lines.
+func (c CommentLines) FindDerives(identity string) ([]*Derive, CommentLines) {
+	remain := make(CommentLines, 0, len(c))
+	ret := make([]*Derive, 0, len(c))
+	for _, s := range c {
+		if m, err := Match(trimRedundance(s)); err != nil {
+			remain = append(remain, s)
+		} else if m.Identity == identity {
+			ret = append(ret, m)
+		}
+	}
+	return ret, remain
+}
+
+func (c *CommentLines) Append(s string) CommentLines {
+	if !strings.HasPrefix(s, "//") {
+		s = "// " + strings.TrimSpace(s)
+	}
+	*c = append(*c, s)
+	return *c
+}
+
+// String formats the comments by inserting // to the start of each line,
+// ensuring that there is a trailing newline.
+// An empty comment is formatted as an empty string.
+func (c CommentLines) String() string {
+	if len(c) == 0 {
+		return ""
+	}
+	b := &strings.Builder{}
+	for i, line := range c {
+		b.WriteString(line)
+		if i+1 < len(c) {
+			b.WriteByte('\n')
+		}
+	}
+	return b.String()
+}
+
+// LineString one line string.
+// String formats the comments by inserting // to the start,
+// the next multi line to trim the start //, join with `, ` .
+// An empty comment is formatted as an empty string.
+func (c CommentLines) LineString() string {
+	if len(c) == 0 {
+		return ""
+	}
+	b := &strings.Builder{}
+	for i, line := range c {
+		b.WriteString(trimRedundance(line))
+		if i+1 < len(c) {
+			b.WriteString(", ")
+		}
+	}
+	return b.String()
+}
+
+// trimRedundance prefix `//` and then trimRedundance leading and trailing whitespace.
+func trimRedundance(s string) string {
+	return strings.TrimSpace(strings.TrimPrefix(s, "//"))
+}