Go - you're my type - Defined Types - methods

Head First Go
楽天ブックス 紀伊國屋書店

開発環境

• macOS Mojave - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Go (プログラミング言語)

Head First Go (Jay McGavren(著)、O'Reilly Media)のChapter 9(you're my type - Defined Types)、Exercise(278)の解答を求めてみる。

コード

sample3_test.go

package main

import "testing"

func TestToMillilitrs(t *testing.T) {
 l := Liters(3)
 want := MilliLiters(3000)
 got := l.ToMilliLiters()
 if got != want {
  t.Errorf("got %f, want %f", got, want)
 }
}

func TestToLiters(t *testing.T) {
 ml := MilliLiters(500)
 want := Liters(0.5)
 got := ml.ToLiters()
 if got != want {
  t.Errorf("got %f, want %f", got, want)
 }
}

sample3.go

package main

type Liters float64
type MilliLiters float64

func (l Liters) ToMilliLiters() MilliLiters {
 return MilliLiters(l * 1000)
}
func (m MilliLiters) ToLiters() Liters {
 return Liters(m / 1000)
}
func main() {}

入出力結果(Bash、cmd.exe(コマンドプロンプト)、Terminal)

$ go test
# _/.../go/Head_First_Go/ch9/sample3 [_/.../go/Head_First_Go/ch9/sample3.test]
./sample3_test.go:6:7: undefined: Liters
./sample3_test.go:15:8: undefined: MilliLiters
FAIL _/.../go/Head_First_Go/ch9/sample3 [build failed]
$ go test
# _/.../go/Head_First_Go/ch9/sample3 [_/.../go/Head_First_Go/ch9/sample3.test]
./sample3_test.go:8:10: l.ToMilliLiters undefined (type Liters has no field or method ToMilliLiters)
./sample3_test.go:17:11: ml.ToLiters undefined (type MilliLiters has no field or method ToLiters)
FAIL _/.../go/Head_First_Go/ch9/sample3 [build failed]
$ go test
# _/.../go/Head_First_Go/ch9/sample3 [_/.../go/Head_First_Go/ch9/sample3.test]
./sample3_test.go:9:9: invalid operation: got != want (mismatched types MilliLiters and float64)
./sample3_test.go:18:9: invalid operation: got != want (mismatched types Liters and float64)
FAIL _/.../go/Head_First_Go/ch9/sample3 [build failed]
$ go test
PASS
ok   _/.../go/Head_First_Go/ch9/sample3 0.005s
$