tour of goの例題

tour_of_go_8.go

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	var z float64 = 1

	for i := 0; i < 10; i++ {
		z = z - ((z*z - x) / (2 * z))
	}

	return z
}

func Sqrt2(x float64) float64 {
	var z float64 = 1
	var loop_count = 1
	var threshold = 0.000000000000001
	for {
		result := z - ((z*z - x) / (2 * z))
		if math.Abs(z-result) < threshold {
			break
		}
		z = result
		loop_count++
	}
	fmt.Println("loop_count is", loop_count)
	return z
}

func MathSqrt(x float64) float64 {
	return math.Sqrt(x)
}

func main() {
	fmt.Println(Sqrt(15125432))
	fmt.Println(Sqrt2(15125432))
	fmt.Println(MathSqrt(15125432))
	/*
	15110.695509529038
	loop_count is 18
	3889.1428361529743
	3889.1428361529743
	*/
}