// +build ignore,OMIT package main import ( "fmt" "sort" ) type Organ struct { Name string Weight Grams } func (o *Organ) String() string { return fmt.Sprintf("%v (%v)", o.Name, o.Weight) } type Grams int func (g Grams) String() string { return fmt.Sprintf("%dg", int(g)) } type Organs []*Organ func (s Organs) Len() int { return len(s) } func (s Organs) Swap(i, j int) { s[i], s[j] = s[j], s[i] } type ByName struct{ Organs } func (s ByName) Less(i, j int) bool { return s.Organs[i].Name < s.Organs[j].Name } type ByWeight struct{ Organs } func (s ByWeight) Less(i, j int) bool { return s.Organs[i].Weight < s.Organs[j].Weight } func main() { s := []*Organ{ {"brain", 1340}, {"heart", 290}, {"liver", 1494}, {"pancreas", 131}, {"spleen", 162}, } // START OMIT sort.Sort(Reverse(ByWeight{s})) // HL printOrgans("Organs by weight (descending)", s) sort.Sort(Reverse(ByName{s})) // HL printOrgans("Organs by name (descending)", s) // STOP OMIT } func printOrgans(t string, s []*Organ) { fmt.Printf("%s:\n", t) for _, o := range s { fmt.Printf(" %v\n", o) } } func Reverse(data sort.Interface) sort.Interface { return &reverse{data} } type reverse struct{ sort.Interface } func (r reverse) Less(i, j int) bool { return r.Interface.Less(j, i) // HL }