Increment and decrement in Go - Mini Project: Build & Apply

Increment and Decrement in Go

📖 Scenario: Imagine you are managing a small store's inventory. You want to keep track of the number of apples you have. Sometimes you sell an apple, so the count goes down. Sometimes you get new apples delivered, so the count goes up.

🎯 Goal: You will create a program that starts with a certain number of apples, then increases and decreases the count using increment and decrement operations.

📋 What You'll Learn

Create a variable to hold the number of apples

Create a variable to hold the number of apples delivered

Use increment and decrement operators to update the apple count

Print the final number of apples

💡 Why This Matters

🌍 Real World

Keeping track of inventory counts in stores or warehouses often requires adding and subtracting items.

💼 Career

Understanding how to update values with increments and decrements is a basic skill for programming tasks like counters, loops, and managing quantities.

1

Create the initial apple count

Create a variable called apples of type int and set it to 10.

Go

# Create a variable called apples of type int and set it to 10
// Your code here

Hint

Use apples := 10 to create and set the variable.

2

Add the number of apples delivered

Create a variable called delivery of type int and set it to 5.

Go

package main

import "fmt"

func main() {
    apples := 10
    // Create a variable called delivery of type int and set it to 5
    // Your code here
}

Hint

Use delivery := 5 to create and set the variable.

3

Update the apple count using increment and decrement

Increase apples by delivery using the += operator. Then decrease apples by 3 using the -= operator.

Go

package main

import "fmt"

func main() {
    apples := 10
    delivery := 5
    // Increase apples by delivery
    // Decrease apples by 3
    // Your code here
}

Hint

Use apples += delivery to add and apples -= 3 to subtract.

4

Print the final number of apples

Use fmt.Println to print the value of apples.

Go

package main

import "fmt"

func main() {
    apples := 10
    delivery := 5
    apples += delivery
    apples -= 3
    // Print the final number of apples
    // Your code here
}

Hint

Use fmt.Println(apples) to show the final count.

Practice

1. What does the expression i++ do in Go?

easy

A. Decreases the value of i by 1

B. Increases the value of i by 1

C. Multiplies the value of i by 2

D. Divides the value of i by 2

Solution

1. Step 1: Understand the operator meaning

   The ++ operator in Go adds 1 to the variable it is used on.

2. Step 2: Apply to variable i

   Using i++ increases the value of i by exactly 1.

3. Final Answer:

   Increases the value of i by 1 -> Option B

4. Quick Check:

   i++ means add 1 [OK]

Hint: Remember ++ means add one, -- means subtract one [OK]

Common Mistakes:

• Confusing ++ with --
• Thinking ++ multiplies or divides
• Using ++ as a function

2. Which of the following is the correct syntax to decrease a variable count by 1 in Go?

easy

A. count--

B. --count

C. count++

D. count =- 1

Solution

1. Step 1: Identify decrement syntax in Go

   In Go, variable-- is the correct way to subtract 1 from a variable.

2. Step 2: Check each option

   count-- uses count--, which is correct. --count is invalid prefix decrement in Go. count++ increases count. count =- 1 is invalid syntax.

3. Final Answer:

   count-- -> Option A

4. Quick Check:

   Use -- to subtract one [OK]

Hint: Use -- to subtract one, not =- [OK]

Common Mistakes:

• Using --count instead of count--
• Confusing ++ and --
• Using count += 1 to decrement

3. What is the output of this Go code?

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

medium

A. Syntax error

B. 5

C. 7

D. 6

Solution

1. Step 1: Trace the increments and decrements

   Start with x = 5. Then x++ makes x = 6. Then x-- makes x = 5 again. Then x++ makes x = 6.

2. Step 2: Print the final value

   The final value of x is 6, so fmt.Println(x) prints 6.

3. Final Answer:

   6 -> Option D

4. Quick Check:

   5 +1 -1 +1 = 6 [OK]

Hint: Add and subtract step by step to find final value [OK]

Common Mistakes:

• Ignoring one increment or decrement
• Thinking increments happen before assignment
• Confusing output with syntax error

4. Find the error in this Go code snippet:

package main
func main() {
  var n int = 10
  n++
  n--
  n = n++
}

medium

A. Assigning n = n++ causes a compile error

B. n-- cannot be used on integers

C. Using n++ as a statement is invalid

D. Variable n must be declared without type

Solution

1. Step 1: Understand usage of n++ in Go

   In Go, n++ and n-- are statements that increment or decrement n by 1. They cannot be used as expressions.

2. Step 2: Analyze the assignment n = n++

   Assigning n = n++ tries to use n++ as a value, which is invalid in Go and causes a compile error.

3. Final Answer:

   Assigning n = n++ causes a compile error -> Option A

4. Quick Check:

   n++ is a statement, not an expression [OK]

Hint: Remember n++ can't be assigned; it's a statement only [OK]

Common Mistakes:

• Trying to assign n = n++
• Thinking n-- is invalid on int
• Ignoring Go's statement-only rule for ++/--

5. You want to count down from 3 to 1 using a for loop in Go. Which code correctly uses decrement to do this?

for i := 3; i > 0; ??? {
  fmt.Println(i)
}

hard

A. i += 1

B. i++

C. i--

D. --i

Solution

1. Step 1: Understand the loop goal

   The loop should count down from 3 to 1, so i must decrease each time.

2. Step 2: Choose the correct decrement expression

   Using i-- decreases i by 1 each loop, matching the goal. Options A, B, and C are wrong: A and B increase i, C is invalid prefix --i in Go.

3. Final Answer:

   i-- -> Option C

4. Quick Check:

   Use i-- to count down in loops [OK]

Hint: Use i-- to count down, i++ to count up [OK]

Common Mistakes:

• Using i++ when counting down
• Using i += 1 instead of i--
• Confusing decrement syntax in for loops