An answer of the exercise: Slices on a tour of Go

answer_pic.go

package main

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

func Pic(dx, dy int) [][]uint8 {
	// Allocate two-dimensioanl array.
	a := make([][]uint8, dy)
	for i := 0; i < dy; i++ {
		a[i] = make([]uint8, dx)
	}
	
	// Do something.
	for i := 0; i < dy; i++ {
		for j := 0; j < dx; j++ {
			switch {
			case j % 15 == 0:
				a[i][j] = 240
			case j % 3 == 0:
				a[i][j] = 120
			case j % 5 == 0:
				a[i][j] = 150
			default:
				a[i][j] = 100
			}
		}
	}	
	return a
}

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

 package main

 import "golang.org/x/tour/pic"

 func Pic(dx, dy int) [][]uint8 {

 slice:= make([][]uint8, dy, dy)
 for y, _ := range slice {
	slice[y] = make([]uint8, dx)
	for x:= range slice {
		i := uint8(y)
		j := uint8(x)
		slice[i][j] = (j * j * 100) + (i * i * 100)
	}
}
 return slice
} 
func main() {
      pic.Show(Pic)
}

package main

import (
    "golang.org/x/tour/pic"
    "math"
)

func Pic(dx, dy int) [][]uint8 {
    bitmap := make([][]uint8, dy)
    
    for i := 0; i < dy; i++ {
	bitmap[i] = make([]uint8, dx)
    }
	
    for i := 0; i < dy; i++ {
	for j := 0; j < dx; j++ {
	    bitmap[i][j] = uint8(math.Sqrt(float64(i)) * .01 * float64(i * j)) >> 2
	}
    }
	
    return bitmap
}

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