Go sort a slice of runes?

Question

I'm having trouble sorting strings by character (to check whether two strings are anagrams, I want to sort both of them, and check for equality).

I can get a []rune representation of the string s like this:

runes := make([]rune, len(s)) 
copy(runes, []rune(s))

And I can sort ints like this

someInts := []int{5, 2, 6, 3, 1, 4} // unsorted
sort.Ints(someInts)

But rune is just an alias for int32 so I should be able to call

sort.Ints(runes) 

However, I get the error:

cannot use runes (type []rune) as type []int in function argument

So... how do I sort a slice of int32, int64, or int*?

EDIT: I did get my runes sorted, but boy, this is ugly.

type RuneSlice []rune

func (p RuneSlice) Len() int           { return len(p) }
func (p RuneSlice) Less(i, j int) bool { return p[i] < p[j] }
func (p RuneSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }

func sorted(s string) string {
    runes := []rune(s)
    sort.Sort(RuneSlice(runes))
    return string(runes)
}

So basically if you have a slice of whatever, you'll have to wrap it in a type that implements sort.Interface. All those implementations will have the exact same method bodies (like sort.IntSlice and sort.Float64Slice). If this is really how ugly this has to be then why didn't they provide these WhateverSlice wrappers in the sort package? The lack of generics start to hurt very badly now. There must be a better way of sorting things.

Answer 1

Use sort.Sort(data Interface) and implement sort.Interface, see the examples on package documentation.

You cannot use rune which is int32 as int. Check the comment of int.

int is a signed integer type that is at least 32 bits in size. It is a distinct type, however, and not an alias for, say, int32.

Answer 2

Note: Go 1.8 will introduce helpers for sorting slices.
See issue 16721 and commit 22a2bdf by Brad Fitzpatrick

var strings = [...]string{"", "Hello", "foo", "bar", "foo", "f00", "%*&^*&^&", "***"}

func TestSlice(t *testing.T) {
    data := strings
    Slice(data[:], func(i, j int) bool {
        return data[i] < data[j]
    })
}