I'm looking at the sort.Reverse code:
type reverse struct {
// This embedded Interface permits Reverse to use the methods of
// another Interface implementation.
Interface
}
// Less returns the opposite of the embedded implementation's Less method.
func (r reverse) Less(i, j int) bool {
return r.Interface.Less(j, i)
}
// Reverse returns the reverse order for data.
func Reverse(data Interface) Interface {
return &reverse{data}
}
As far as I understand reverse implements Interface (and overrides Less) and *reverse does not implement Interface. Why does Reverse return *reverse (which somehow is Interface)?
For your comment:
As far as I understand reverse implements Interface (and overrides Less)
There is no method overriding in Golang. It is not overriding Less. It is implementing Less of Interface which is an interface type:
type Interface interface {
// Len is the number of elements in the collection.
Len() int
// Less reports whether the element with
// index i should sort before the element with index j.
Less(i, j int) bool
// Swap swaps the elements with indexes i and j.
Swap(i, j int)
}
For the question asked:
Why does Reverse return *reverse (which somehow is Interface)
Because to change the order of the data it should be an address of the reverse struct. That's why it is *reverse. Now you can pass any type implementing Interface interface. And for implementing the Interface you should implement all the methods defined inside Interface.
type IntSlice []int
func (p IntSlice) Len() int { return len(p) }
func (p IntSlice) Less(i, j int) bool { return p[i] < p[j] }
func (p IntSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
In above case you can see that IntSlice implements the Interface. Hence you can pass the Intslice as an argument to Reverse.
As an example you can also implement using Float values as:
package main
import (
"fmt"
"sort"
)
func main() {
//s := []int{5, 2, 6, 3, 1, 4} // unsorted
s1 := []float64{5.2, 2.6, .6, .03, 2.1 } // unsorted
sort.Sort(sort.Reverse(sort.Float64Slice(s1)))
fmt.Println(s1)
}