Assignment operators in Go - Mini Project: Build & Apply

Assignment Operators in Go

📖 Scenario: You are helping a small shop keep track of the number of items in stock. You will use assignment operators to update the stock count as items are added or sold.

🎯 Goal: Build a Go program that uses assignment operators to update the stock count of a product step-by-step.

📋 What You'll Learn

Create a variable to hold the initial stock count

Create a variable to hold the number of items added or sold

Use assignment operators to update the stock count

Print the final stock count

💡 Why This Matters

🌍 Real World

Shops and businesses often need to update stock counts quickly as items are added or sold.

💼 Career

Understanding assignment operators is essential for writing clear and efficient code in many programming jobs.

1

Create the initial stock count

Create an int variable called stock and set it to 50.

Go

// Your code here

Hint

Use := to declare and assign the variable stock.

2

Create a variable for items added

Create an int variable called added and set it to 20.

Go

package main

import "fmt"

func main() {
    stock := 50
    // Your code here
}

Hint

Declare added using := and assign 20.

3

Update stock using assignment operators

Use the += assignment operator to add added to stock.

Go

package main

import "fmt"

func main() {
    stock := 50
    added := 20
    // Your code here
}

Hint

Use stock += added to increase stock by added.

4

Print the final stock count

Use fmt.Println to print the value of stock.

Go

package main

import "fmt"

func main() {
    stock := 50
    added := 20
    stock += added
    // Your code here
}

Hint

Use fmt.Println(stock) to show the updated stock count.

Practice

1. What does the += operator do in Go?

easy

A. Subtracts the right value from the left variable and stores the result

B. Assigns the right value to the left variable without any operation

C. Adds the right value to the left variable and stores the result in the left variable

D. Multiplies the left variable by the right value and stores the result

Solution

1. Step 1: Understand the operator meaning

   The += operator adds the right-hand side value to the left-hand side variable.

2. Step 2: Understand the assignment effect

   It then stores the sum back into the left-hand side variable, updating its value.

3. Final Answer:

   Adds and assigns the sum to the left variable -> Option C

4. Quick Check:

   += means add and assign [OK]

Hint: Think: add right value to left and save [OK]

Common Mistakes:

• Confusing += with simple assignment =
• Thinking it subtracts instead of adds
• Mixing it with multiplication or division

2. Which of the following is the correct syntax to multiply variable x by 5 and store the result back in x?

easy

A. x =* 5

B. x = x *=

C. x = *5

D. x *= 5

Solution

1. Step 1: Identify correct compound assignment syntax

   In Go, the multiplication assignment operator is *=, used as x *= 5.

2. Step 2: Check each option for syntax correctness

   x *= 5 matches the correct syntax; others are invalid or cause errors.

3. Final Answer:

   x *= 5 -> Option D

4. Quick Check:

   Use *= for multiply and assign [OK]

Hint: Remember operator before = for compound assignment [OK]

Common Mistakes:

• Placing = before * (like =*)
• Missing space causing syntax errors
• Using incomplete expressions like x = *5

3. What is the output of the following Go code?

package main
import "fmt"
func main() {
  a := 10
  a += 5
  a -= 3
  fmt.Println(a)
}

medium

A. 12

B. 15

C. 8

D. 10

Solution

1. Step 1: Calculate after addition

   Starting with a = 10, after a += 5, a becomes 15.

2. Step 2: Calculate after subtraction

   Then a -= 3 subtracts 3, so a becomes 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Apply operations step-by-step to variable [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing += and -= effects
• Ignoring initial value of variable

4. Identify the error in this Go code snippet:

package main
import "fmt"
func main() {
  var x int = 10
  x + = 5
  fmt.Println(x)
}

medium

A. The operator + = has a space and is invalid

B. Variable x is not declared

C. Missing semicolon after var declaration

D. fmt package is not imported

Solution

1. Step 1: Check operator syntax

   The operator += must not have spaces; + = is invalid syntax.

2. Step 2: Verify other code parts

   Variable x is declared correctly, semicolons are optional in Go, and the fmt package is imported.

3. Final Answer:

   Operator + = has a space and is invalid -> Option A

4. Quick Check:

   No spaces in compound operators [OK]

Hint: Compound operators have no spaces (e.g., +=) [OK]

Common Mistakes:

• Adding spaces inside operators
• Assuming semicolons are always required
• Confusing the compound operator with separate + and = operations

5. Given the code below, what will be the final value of total?

package main
import "fmt"
func main() {
  total := 20
  total /= 4
  total *= 3
  total %= 5
  fmt.Println(total)
}

hard

A. 3

B. 0

C. 4

D. 5

Solution

1. Step 1: Perform division assignment

   total = 20, after total /= 4, total becomes 5 (integer division).

2. Step 2: Perform multiplication assignment

   Then total *= 3 makes total 15.

3. Step 3: Perform modulus assignment

   total %= 5 calculates remainder of 15 divided by 5, which is 0.

4. Step 4: Re-check calculations

   Integer division 20/4 = 5, 5*3=15, 15%5=0.

5. Final Answer:

   0 -> Option B

6. Quick Check:

   20/4=5, 5*3=15, 15%5=0 [OK]

Hint: Apply each operator stepwise, watch integer division [OK]

Common Mistakes:

• Forgetting integer division truncates decimals
• Mixing up modulus with division
• Calculating modulus before multiplication