Assignment operators in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of assignment operators in Go?

Assignment operators in Go are used to assign values to variables. They can also combine an operation with assignment, like adding a value and then assigning the result.

beginner

What does the operator += do in Go?

The operator += adds the right-hand value to the left-hand variable and then assigns the result back to that variable. For example, x += 3 means x = x + 3.

beginner

Explain the difference between = and *= in Go.

The = operator assigns a value directly to a variable. The *= operator multiplies the variable by a value and assigns the result back to the variable. For example, x *= 2 means x = x * 2.

intermediate

Can you use assignment operators with all data types in Go?

Assignment operators work with numeric types like int, float, and also with strings for the = operator. Operators like += work with numbers and strings (for concatenation). They do not work with all types, like structs or arrays directly.

beginner

What happens if you write x -= 5 in Go?

The value 5 is subtracted from the current value of x, and the result is stored back in x. It is the same as writing x = x - 5.

What does the operator /= do in Go?

A Divides the variable by a value and assigns the result back

B Assigns a new value without any operation

C Adds a value to the variable

D Subtracts a value from the variable

The /= operator divides the variable by the right-hand value and assigns the result back to the variable.

Which operator would you use to add 10 to a variable x in Go?

A x += 10

B x =+ 10

C x =- 10

D x -= 10

The += operator adds the right-hand value to the variable and assigns the result back.

What is the result of this code snippet? var x = 5 x *= 3

A x is 8

B x is 2

C x is 15

D x is 5

The *= operator multiplies x by 3, so x becomes 15.

Which assignment operator can be used to concatenate strings in Go?

A -=

B +=

C *=

D /=

The += operator can concatenate strings by adding the right string to the left.

Is this statement true or false? "The = operator can be used to assign a value to a variable."

A Only for strings

B False

C Only for numbers

D True

The = operator assigns any compatible value to a variable.

Explain how assignment operators like += and *= work in Go with an example.

Think about how you can shorten x = x + 3 using an assignment operator.

List common assignment operators in Go and describe what each does.

Start with simple ones like = and +=, then mention others that combine operations with assignment.

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