Golang : Calculate diameter, circumference, area, sphere surface and volume
Let's travel back to high school for a while and learn some physics. We will learn how to calculate a circle's area, diameter, circumference, sphere surface and sphere volume the proper way.
I saw many programmers calculate the sphere volume the wrong way in Golang. While the result might appear to be correct mathematically, but wrong. A simple division by float or integer will make a big difference in the sphere volume result.
4/3
is not the same as 4/3.0
. The code below will demonstrate the differences and as a programmer, it is our job to look out for a simple mistake such as this. You never know in future, some one's life might depend on your code.
Here you go!
package main
import (
"fmt"
"math"
)
var (
radius, diameter, circumference, area, sphereSurface, sphereVolume float64
)
func main() {
fmt.Println("Enter the radius of a circle (in meter): ")
_, err := fmt.Scanf("%f", &radius)
if err != nil {
fmt.Println(err)
}
fmt.Println("You have entered radius of : ", radius)
diameter = 2 * radius
circumference = 2 * math.Pi * radius
area = math.Pi * math.Pow(radius, 2)
sphereSurface = 4 * math.Pi * math.Pow(radius, 2)
// Go to be careful here, casting float64 over 4/3 is pointless
// because 4/3 is still 1
// The correct way is to do 4.0/3.0
sphereVolume = float64((4.0 / 3.0)) * (math.Pi * math.Pow(radius, 3))
// this will give wrong result
//sphereVolume = 4 / 3 * math.Pi * radius * radius * radius
fmt.Println("Diameter (m) : ", diameter)
fmt.Println("Circumference (m): ", circumference)
fmt.Println("Area (m2) : ", area)
fmt.Println("Sphere surface (m2) : ", sphereSurface)
fmt.Println("Sphere volume (m3) [correct way] : ", sphereVolume)
sphereVolume = 4 / 3 * math.Pi * radius * radius * radius // <--- WRONG!
fmt.Println("Sphere volume (m3) [wrong way] : ", sphereVolume)
// compare your calculation result with
// result from http://www.rkm.com.au/CALCULATORS/CALCULATOR-circle-sphere.html
// and http://www.calculatorsoup.com/calculators/geometry-solids/sphere.php
}
Output:
Enter the radius of a circle (in meter):
5
You have entered radius of : 5
Diameter (m) : 10
Circumference (m): 31.41592653589793
Area (m2) : 78.53981633974483
Sphere surface (m2) : 314.1592653589793
Sphere volume (m3) [correct way] : 523.5987755982987
Sphere volume (m3) [wrong way] : 392.69908169872417
References:
http://www.rkm.com.au/CALCULATORS/CALCULATOR-circle-sphere.html
See also : Golang : Find change in a combination of coins example
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+44.1k Golang : Marshal and unmarshal json.RawMessage struct example
+3.7k Nginx and PageSpeed build from source CentOS example
+23.6k Golang : Storing cookies in http.CookieJar example
+10.3k Golang : Find and draw contours with OpenCV example
+4.1k Python : Convert(cast) bytes to string example
+6.7k Golang : get the current working directory of a running program
+8k Golang : Play .WAV file from command line
+6.3k Golang : Create zip/ePub file without compression(use Store algorithm)
+3.7k Golang : Experimental Jawi programming language
+15.7k Golang : Check if IP address is version 4 or 6
+3.8k Golang : A program that contain another program and executes it during run-time