For a blog post in Hashnode where I give a couple examples of easy projects so that devs can see the difference between their current favorite language and Golang. It's also a quick and fun test for myself and could be for others as well.

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What I want to do

Create a simple math quiz that randomly gives you an addition, subtraction, multiplication, or division question.

• generate 2 random numbers (num1, num2)
• have the result (res) be equal to the numbers
• keep all numbers less than or equal to 100
  • May increase limit later, doing this just for simplicity right now

My Process

Starting With Addition

• Create a min and max value

var min = 0
var max = 100

• Create the 2 nums with random values. Found in docs

var num1 = rand.Intn(max-min) + min
var num2 = rand.Intn(max-min) + min

• Have a variable that's the result of the 2 nums being added
• Print the 2 nums
• Let user input their answer
• If the answer is correct then print Correct!. Else print Sorry, that's incorrect.

var addRes int

fmt.Println(num1, "+", num2)

fmt.Println("Your answer:")
fmt.Scanln(&addRes)

if addRes == num1 + num2 {
	fmt.Println("Correct!")
	return
} else {
	fmt.Println("Sorry, that's incorrect")
	return
}

This is what it looks like so far:

func main() {
	var min = 0
	var max = 100

	var num1 = rand.Intn(max-min) + min
	var num2 = rand.Intn(max-min) + min

	var addRes int

	fmt.Println(num1, "+", num2)

	fmt.Println("Your answer:")
	fmt.Scanln(&addRes)

	if addRes == num1 + num2 {
		fmt.Println("Correct!")
		return
	} else {
		fmt.Println("Sorry, that's incorrect")
		return
	}
}

Testing the application.

The initial test works! However, it will always print out 81+87. We need to randomize the numbers each time.

• Change the logic of num1 and num2
• Found an article that describes how to do this with the time package
  • the docs had something similar but for some reason it couldn't click in my brain until I saw this one
• Delete the min and max variables and add the Unix randomizer

rand.Seed(time.Now().UnixNano())

var num1 = rand.Intn(100)
var num2 = rand.Intn(100)

Testing the application.

It works as intended. If you just want the quiz to be addition only this is good enough, however, I want to include subtraction, multiplication, and division.

Before we can move on, I want to separate the logic for the addition problem into it's own function. If we don't do this before adding in the other logic, the main func will look horrendous.

func main() {
	rand.Seed(time.Now().UnixNano())

	var num1 = rand.Intn(100)
	var num2 = rand.Intn(100)

	addition(num1, num2)
}

func addition(num1 int, num2 int) {
	var addRes int

	fmt.Println(num1, "+", num2)

	fmt.Println("Your answer:")
	fmt.Scanln(&addRes)

	if addRes == num1 + num2 {
		fmt.Println("Correct!")
		return
	} else {
		fmt.Println("Sorry, that's incorrect")
		return
	}
}

Now that addition is in it's own function, we can start on the other math questions.

Subtraction, Multiplication, and Division

• The subtraction function is almost the exact same as addition, but swapping + for -.
• Then in the main func, swap addition(num1, num2) for subtraction(num1, num2)
• Then for multiplication it will look similar... Blah, blah, blah you get the idea

Testing func subtraction.

Testing func division and func multiplication

Randomizing Which Function Gets Called

• We need a way to randomize which function gets called back into the main function
• When I was looking in the golang docs I saw an example of a for loop randomizing integers in an array
• Since there are 4 questions, maybe I could create an array of 4 values, loop over those values with a random number, and if the result of a particular index in the array equals a certain number it would return the associated function?

func randomize(num1 int, num2 int) {
	var arr [4]int

	rand.Seed(time.Now().UnixNano())
	for i := 0; i <= 3; i++ {
		arr[i] = rand.Intn(4)
	}

	var res int

	if res == arr[0] {
		multiplication(num1, num2)
		return
	} else if res == arr[1] {
		division(num1, num2)
		return
	} else if res == arr[2] {
		addition(num1, num2)
		return
	} else if res == arr[3] {
		subtraction(num1, num2)
		return
	} 
}

• Then call randomize(num1, num2) inside of the main func and see if it works
• Annndddd... nothing happened :/
• (A bit of foreshadowing to a paragraph later; this is why you should print to the console when you're in doubt and walk away from the computer for a few mins when you're stuck)
• I'm going to try again but this time remove return from the if else statements

Testing func randomize

• So it works sometimes but doesn't work other times
• Maybe if I change arr[i] = rand.Intn(4) to arr[i] = rand.Intn(3) I can get it to work every time?

Testing func randomize again

• So it works, however I found an interesting bug
• When I input for the result of 81 / 0 it gave me an error
• That's because a number can't be divided by 0
• I tried this on my IPhone's calculator and it said "Error"
• This can be avoided by changing the parameters of calling the division function to else if res == arr[1] && num1 != 0 && num2 != 0
• After taking a 15 min break and eating some ice cream, I realized the way it chooses which question to ask is kind of dumb

Refactoring Randomization

• For some reason I thought res would equal to... honestly, now that I'm sitting back down and typing out my reasoning, I don't know what I thought it was equal to. In reality it's equal to 0, so the first index in the array to equal 0 will be called
• That's a problem because if the array is [0 0 1 1], multiplication will be called because it's first in the stack
• Also, if the array is [1 1 2 2] then nothing will be called
  • This is why it didn't work earlier, not because it had return in the if else statements
• I still need a way to evenly decide which question will be asked
• Since there are 4 questions, each should have about a 25% chance of being asked
• What if, instead of having an array of four values that could equal anything from 0-3, the array only has one value that could equal anything from 0-99?
  • if the value is anywhere from 0-24 it would return multiplication
  • 25-49 would be division
  • 50-74 would be addition
  • 75-99 would be subtraction
• And in case num1 or num2 is equal to 0, it'll return addition
  • It won't be a perfect 25% chance for division and addition, but it's very close, and avoids errors

func randomize(num1 int, num2 int) {
	var arr [1]int

	rand.Seed(time.Now().UnixNano())
	for i := 0; i <= 0; i++ {
		arr[i] = rand.Intn(100)
	}

	if arr[0] <= 24 {
		multiplication(num1, num2)
		return
	} else if arr[0] >= 25 && arr[0] <= 49 && num1 != 0 && num2 != 0{
		division(num1, num2)
		return
	} else if arr[0] >= 50 && arr[0] <= 74 {
		addition(num1, num2)
		return
	} else if arr[0] >= 75 {
		subtraction(num1, num2)
		return
	} else {
		addition(num1, num2)
		return
	}
}

Testing the result

Finally got it working!!!!

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Ideas to implement later

• Have the program ask for an answer that equals the addition problem, subtraction problem, multiplication problem, and division problem all at once.
  • try implementing Go routines to execute all 4 functions simultaneously