As a simple way to play with functions and loops, implement the square root function using Newton's method. In this case, Newton's method is to approximate Sqrt(x) by picking a starting point z and then repeating: To begin with, just repeat that calculation 10 times and see how close you get to the answer for various values (1, 2, 3, ...). Next,…

sqrt.go

package main

import (
	"fmt"
	"math"
)

const Delta = 0.0001

func Sqrt(x float64) float64 {
	z := 1.0
    	tmp := 0.0
    
    	for {
        	tmp = z - (z * z - x) / 2.0 * z
    		if d := tmp - z; math.Abs(d) < Delta {
        		return tmp
        	}
        	z = tmp
    	}
    	return z
}

func main() {
    	attempt := Sqrt(2)
	expected := math.Sqrt(2)
	fmt.Printf("attempt = %g\n", attempt)
    	fmt.Printf("expected = %g\n", expected)
    	fmt.Printf("error = %g\n", attempt - expected)
}