An answer for http://go-tour-jp.appspot.com/#35

a35.go

//http://go-tour-jp.appspot.com/#35
package main

import "code.google.com/p/go-tour/pic"

func f0(x, y int) uint8 {return uint8(x^y)}
func f1(x, y int) uint8 {return uint8((x+y)/2)}
func f2(x, y int) uint8 {return uint8(x*y)}
    
func Pic(dx, dy int) [][]uint8 {
    f := f0
    
    a := make([][]uint8, dy)
    for i := 0; i < len(a); i++ {
	r := make([]uint8, dx)
	for j := 0; j < len(r); j++ {
            r[j] = f(j, i)
        }
        a[i] = r
    }
    return a
}

func main() {
    pic.Show(Pic)
}

私が書くならこうかな。

for i, _ := range a {
    // ...
    a[i] = r
}