Increment and decrement in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the increment operator ++ do in Go?

It increases the value of a variable by 1. For example, i++ adds 1 to i.

beginner

How do you decrease a variable's value by 1 in Go?

Use the decrement operator --. For example, i-- subtracts 1 from i.

intermediate

Can you use ++ or -- as part of an expression in Go?

No. In Go, ++ and -- are statements, not expressions. You cannot write j = i++ like in some other languages.

beginner

Show a simple Go code snippet that increments a variable count by 1.

<pre>package main
import "fmt"

func main() {
    count := 0
    count++
    fmt.Println(count) // Output: 1
}</pre>

intermediate

Why can't you write ++i or --i in Go?

Go does not support prefix increment or decrement operators. Only postfix i++ and i-- are allowed.

What does i++ do in Go?

A Divides i by 2

B Subtracts 1 from i

C Adds 1 to i

D Multiplies i by 2

i++ increases the value of i by 1.

Which of these is valid in Go?

A i++

B j = i++

C ++i

D j = ++i

Only i++ as a statement is valid. You cannot use ++ as part of an expression.

What happens if you write i-- in Go?

A Syntax error

B i increases by 1

C i is set to zero

D i decreases by 1

i-- subtracts 1 from i.

Can you write ++i in Go?

A No, Go only supports postfix <code>i++</code>

B Yes, it works like in C

C Yes, but only inside loops

D No, Go does not support increment operators

Go only supports postfix increment and decrement operators.

Which of the following is a correct way to increment count in Go?

A count = count + 1

B Both A and B

C count++

D count += 2

You can increment by 1 using either count = count + 1 or count++.

Explain how increment and decrement operators work in Go and how they differ from other languages.

Think about how you write <code>i++</code> and if you can use it inside other expressions.

Write a short Go code snippet that declares a variable and increments it twice, then prints the result.

Use <code>var</code> or :=, then <code>++</code>, then <code>fmt.Println</code>.

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