Go - Structs and Interfaces(interface, perimeter method(周囲の長さ), math package, Pi(円周率), Pow(累乗(べき乗)))

Introducing Go

開発環境

• macOS High Sierra - Apple (OS)
• Emacs (Text Editor)
• Go (プログラミング言語)

Introducing Go: Build Reliable, Scalable Programs (Caleb Doxsey (著)、O'Reilly Media)のChapter 7.(Structs and Interfaces)、Exercises(No. 1315)3.を取り組んでみる。

コード(Emacs)

package main

import (
 "fmt"
 "math"
)

type Circle struct {
 x, y, r float64
}
type Rectangle struct {
 x1, y1, x2, y2 float64
}
type Shape interface {
 perimeter() float64
}

func (c *Circle) perimeter() float64 {
 return math.Pi * math.Pow(c.r, 2)
}
func (r *Rectangle) perimeter() float64 {
 a := r.x2 - r.x1
 b := r.y2 - r.y1

 return 2 * (math.Abs(a) + math.Abs(b))
}
func main() {
 c1 := Circle{x: 1, y: 2, r: 1}
 c2 := Circle{3, 4, 5}
 r1 := Rectangle{x1: 1, y1: 2, x2: -1, y2: -2}
 r2 := Rectangle{-1, -2, 1, 2}
 shapes := []Shape{&c1, &c2, &r1, &r2}

 fmt.Println(math.Pi, math.Pow(2, 3))
 
 for _, s := range shapes {
  fmt.Println(s.perimeter())
 }
}

入出力結果(Terminal)

$ go run sample3.go
3.141592653589793 8
3.141592653589793
78.53981633974483
12
12
$