168 lines
4.5 KiB
Go
168 lines
4.5 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
|
|
|
// See page 187.
|
|
|
|
// Sorting sorts a music playlist into a variety of orders.
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"os"
|
|
"sort"
|
|
"text/tabwriter"
|
|
"time"
|
|
)
|
|
|
|
//!+main
|
|
type Track struct {
|
|
Title string
|
|
Artist string
|
|
Album string
|
|
Year int
|
|
Length time.Duration
|
|
}
|
|
|
|
var tracks = []*Track{
|
|
{"Go", "Delilah", "From the Roots Up", 2012, length("3m38s")},
|
|
{"Go", "Moby", "Moby", 1992, length("3m37s")},
|
|
{"Go Ahead", "Alicia Keys", "As I Am", 2007, length("4m36s")},
|
|
{"Ready 2 Go", "Martin Solveig", "Smash", 2011, length("4m24s")},
|
|
}
|
|
|
|
func length(s string) time.Duration {
|
|
d, err := time.ParseDuration(s)
|
|
if err != nil {
|
|
panic(s)
|
|
}
|
|
return d
|
|
}
|
|
|
|
//!-main
|
|
|
|
//!+printTracks
|
|
func printTracks(tracks []*Track) {
|
|
const format = "%v\t%v\t%v\t%v\t%v\t\n"
|
|
tw := new(tabwriter.Writer).Init(os.Stdout, 0, 8, 2, ' ', 0)
|
|
fmt.Fprintf(tw, format, "Title", "Artist", "Album", "Year", "Length")
|
|
fmt.Fprintf(tw, format, "-----", "------", "-----", "----", "------")
|
|
for _, t := range tracks {
|
|
fmt.Fprintf(tw, format, t.Title, t.Artist, t.Album, t.Year, t.Length)
|
|
}
|
|
tw.Flush() // calculate column widths and print table
|
|
}
|
|
|
|
//!-printTracks
|
|
|
|
//!+artistcode
|
|
type byArtist []*Track
|
|
|
|
func (x byArtist) Len() int { return len(x) }
|
|
func (x byArtist) Less(i, j int) bool { return x[i].Artist < x[j].Artist }
|
|
func (x byArtist) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
|
|
|
|
//!-artistcode
|
|
|
|
//!+yearcode
|
|
type byYear []*Track
|
|
|
|
func (x byYear) Len() int { return len(x) }
|
|
func (x byYear) Less(i, j int) bool { return x[i].Year < x[j].Year }
|
|
func (x byYear) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
|
|
|
|
//!-yearcode
|
|
|
|
func main() {
|
|
fmt.Println("byArtist:")
|
|
sort.Sort(byArtist(tracks))
|
|
printTracks(tracks)
|
|
|
|
fmt.Println("\nReverse(byArtist):")
|
|
sort.Sort(sort.Reverse(byArtist(tracks)))
|
|
printTracks(tracks)
|
|
|
|
fmt.Println("\nbyYear:")
|
|
sort.Sort(byYear(tracks))
|
|
printTracks(tracks)
|
|
|
|
fmt.Println("\nCustom:")
|
|
//!+customcall
|
|
sort.Sort(customSort{tracks, func(x, y *Track) bool {
|
|
if x.Title != y.Title {
|
|
return x.Title < y.Title
|
|
}
|
|
if x.Year != y.Year {
|
|
return x.Year < y.Year
|
|
}
|
|
if x.Length != y.Length {
|
|
return x.Length < y.Length
|
|
}
|
|
return false
|
|
}})
|
|
//!-customcall
|
|
printTracks(tracks)
|
|
}
|
|
|
|
/*
|
|
//!+artistoutput
|
|
Title Artist Album Year Length
|
|
----- ------ ----- ---- ------
|
|
Go Ahead Alicia Keys As I Am 2007 4m36s
|
|
Go Delilah From the Roots Up 2012 3m38s
|
|
Ready 2 Go Martin Solveig Smash 2011 4m24s
|
|
Go Moby Moby 1992 3m37s
|
|
//!-artistoutput
|
|
|
|
//!+artistrevoutput
|
|
Title Artist Album Year Length
|
|
----- ------ ----- ---- ------
|
|
Go Moby Moby 1992 3m37s
|
|
Ready 2 Go Martin Solveig Smash 2011 4m24s
|
|
Go Delilah From the Roots Up 2012 3m38s
|
|
Go Ahead Alicia Keys As I Am 2007 4m36s
|
|
//!-artistrevoutput
|
|
|
|
//!+yearoutput
|
|
Title Artist Album Year Length
|
|
----- ------ ----- ---- ------
|
|
Go Moby Moby 1992 3m37s
|
|
Go Ahead Alicia Keys As I Am 2007 4m36s
|
|
Ready 2 Go Martin Solveig Smash 2011 4m24s
|
|
Go Delilah From the Roots Up 2012 3m38s
|
|
//!-yearoutput
|
|
|
|
//!+customout
|
|
Title Artist Album Year Length
|
|
----- ------ ----- ---- ------
|
|
Go Moby Moby 1992 3m37s
|
|
Go Delilah From the Roots Up 2012 3m38s
|
|
Go Ahead Alicia Keys As I Am 2007 4m36s
|
|
Ready 2 Go Martin Solveig Smash 2011 4m24s
|
|
//!-customout
|
|
*/
|
|
|
|
//!+customcode
|
|
type customSort struct {
|
|
t []*Track
|
|
less func(x, y *Track) bool
|
|
}
|
|
|
|
func (x customSort) Len() int { return len(x.t) }
|
|
func (x customSort) Less(i, j int) bool { return x.less(x.t[i], x.t[j]) }
|
|
func (x customSort) Swap(i, j int) { x.t[i], x.t[j] = x.t[j], x.t[i] }
|
|
|
|
//!-customcode
|
|
|
|
func init() {
|
|
//!+ints
|
|
values := []int{3, 1, 4, 1}
|
|
fmt.Println(sort.IntsAreSorted(values)) // "false"
|
|
sort.Ints(values)
|
|
fmt.Println(values) // "[1 1 3 4]"
|
|
fmt.Println(sort.IntsAreSorted(values)) // "true"
|
|
sort.Sort(sort.Reverse(sort.IntSlice(values)))
|
|
fmt.Println(values) // "[4 3 1 1]"
|
|
fmt.Println(sort.IntsAreSorted(values)) // "false"
|
|
//!-ints
|
|
}
|