added sort support

helper.go

@@ -12,6 +12,37 @@ const (
 	anys = string(any)
 )
 
+type less func(i, j int) bool
+
+func reverse(f less) less {
+	return func(i, j int) bool {
+		return f(j, i)
+	}
+}
+
+func index(f Filter, i int, fields []string) (val reflect.Value) {
+	val = reflect.ValueOf(f.Index(i)).FieldByName(fields[0])
+	for j := 1; j < len(fields); j++ {
+		val = val.FieldByName(fields[j])
+	}
+	return
+}
+
+func makeLess(f Filter, fields []string) less {
+	switch index(f, 0, fields).Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16,
+		reflect.Int32, reflect.Int64:
+		return func(i, j int) bool { return index(f, i, fields).Int() < index(f, j, fields).Int() }
+	case reflect.Float32, reflect.Float64:
+		return func(i, j int) bool { return index(f, i, fields).Float() < index(f, j, fields).Float() }
+	case reflect.String:
+		return func(i, j int) bool { return index(f, i, fields).String() < index(f, j, fields).String() }
+	case reflect.Bool:
+		return func(i, _ int) bool { return index(f, i, fields).Bool() }
+	}
+	return nil
+}
+
 func getValue(v reflect.Value) (s string, b bool, err error) {
 	switch v.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16,