Why does sorted "tan" != "ant"?

Question

I'm trying to sort the characters in a string by sorting a slice of the bytes in the string (using sort.Slice). The code I'm using gets the right results sometimes but other times produces results I can't make sense of.

package main

import (
    "fmt"
    "sort"
)

func main() {
    for _, s := range []string{"nat", "tan", "ant"} {
        b := []byte(s)
        sort.Slice(b, func(i int, j int) bool { return s[i] < s[j] })
        fmt.Println(s, string(b))
    }
}

https://play.golang.org/p/bC9QWq7aF3G

I would expect "nat", "tan" and "ant" to all be sorted to "ant", but "tan" is sorted to "atn".

Answer 1

Change your sort.Slice line to:

sort.Slice(b, func(i int, j int) bool { return b[i] < b[j] })

sort.Slice needs your less function to compare values in the slice in order to sort the way you intended. Your bug is that you used s rather than b in your less function.