Logical operators in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the three main logical operators in Go?

The three main logical operators in Go are AND (&&), OR (||), and NOT (!). They help combine or invert boolean values.

beginner

How does the AND (&&) operator work in Go?

The AND operator (&&) returns true only if both conditions are true. If either is false, the result is false.

beginner

What does the OR (||) operator do in Go?

The OR operator (||) returns true if at least one of the conditions is true. It returns false only if both are false.

beginner

Explain the NOT (!) operator in Go.

The NOT operator (!) reverses the value of a boolean. If the value is true, ! makes it false, and if false, ! makes it true.

intermediate

What is short-circuit evaluation in Go's logical operators?

Short-circuit evaluation means Go stops checking conditions as soon as the result is known. For example, in AND (&&), if the first is false, Go skips the second because the result can't be true.

Which operator returns true only if both conditions are true?

A & (bitwise AND)

B || (OR)

C && (AND)

D ! (NOT)

The && operator returns true only when both conditions are true.

What does the expression !(true) evaluate to in Go?

A false

B error

C true

D nil

The NOT operator (!) reverses true to false.

If the first condition in an OR (||) expression is true, what happens next?

A The second condition is checked

B The expression returns true immediately

C The expression returns false

D The program crashes

Go uses short-circuit evaluation and returns true immediately if the first condition in OR is true.

Which operator would you use to check if a condition is NOT true?

A !

B &&

C ||

D ==

The ! operator negates a boolean value.

What is the result of true && false in Go?

A nil

B true

C error

D false

AND (&&) returns true only if both are true; here one is false, so result is false.

Describe how the AND, OR, and NOT logical operators work in Go with simple examples.

Think about true and false combinations and how each operator changes the result.

Explain what short-circuit evaluation means in Go's logical operators and why it is useful.

Consider when Go stops checking conditions early.

Practice

1. Which logical operator in Go means AND and returns true only if both conditions are true?

easy

A. !

B. ||

C. &

D. &&

Solution

1. Step 1: Understand the meaning of logical AND

   The AND operator returns true only when both conditions it connects are true.

2. Step 2: Identify Go's AND operator

   In Go, the AND operator is written as &&, which matches the description.

3. Final Answer:

   && -> Option D

4. Quick Check:

   AND = && [OK]

Hint: AND is &&, OR is ||, NOT is ! [OK]

Common Mistakes:

• Confusing & (bitwise AND) with && (logical AND)
• Mixing OR (||) with AND (&&)
• Using ! as AND operator

2. Which of the following is the correct syntax for the logical NOT operator in Go?

easy

A. not x

B. !x

C. ~x

D. x!

Solution

1. Step 1: Recall Go syntax for logical NOT

   In Go, the logical NOT operator is a single exclamation mark placed before the variable or expression.

2. Step 2: Match options with correct syntax

   !x uses !x, which is the correct syntax for NOT in Go.

3. Final Answer:

   !x -> Option B

4. Quick Check:

   NOT = ! [OK]

Hint: NOT always uses ! before the condition [OK]

Common Mistakes:

• Writing 'not x' like in some other languages
• Using ~ which is bitwise NOT, not logical NOT
• Placing ! after the variable

3. What is the output of this Go code snippet?

package main
import "fmt"
func main() {
    a := true
    b := false
    fmt.Println(a && !b || b)
}

medium

A. true

B. false

C. Syntax error

D. Compilation error

Solution

1. Step 1: Evaluate !b

   b is false, so !b is true.

2. Step 2: Evaluate a && !b

   a is true and !b is true, so a && !b is true.

3. Step 3: Evaluate (a && !b) || b

   true || false is true.

4. Final Answer:

   true -> Option A

5. Quick Check:

   True AND NOT False OR False = True [OK]

Hint: Evaluate NOT first, then AND, then OR [OK]

Common Mistakes:

• Evaluating OR before AND
• Forgetting to negate b
• Assuming false || true is false

4. Identify the error in this Go code snippet:

package main
import "fmt"
func main() {
    x := true
    y := false
    if x & y {
        fmt.Println("Both true")
    }
}

medium

A. Using & instead of && in if condition

B. Missing parentheses around condition

C. fmt.Println syntax error

D. Variable declaration error

Solution

1. Step 1: Check logical operators in if condition

   The code uses & which is bitwise AND, not logical AND.

2. Step 2: Identify correct operator for boolean logic

   Logical AND in Go is &&, so & causes a type error here.

3. Final Answer:

   Using & instead of && in if condition -> Option A

4. Quick Check:

   Logical AND needs &&, not & [OK]

Hint: Use && for logical AND, & is bitwise [OK]

Common Mistakes:

• Using & instead of && for booleans
• Assuming & works like && in conditions
• Ignoring compiler error messages

5. Given a variable score (int), which condition correctly checks if score is between 50 and 100 inclusive using logical operators in Go?

hard

A. score >= 50 || score <= 100

B. score > 50 && score < 100

C. score >= 50 && score <= 100

D. score > 50 || score < 100

Solution

1. Step 1: Understand the range condition

   We want score to be at least 50 and at most 100, so both conditions must be true.

2. Step 2: Choose correct logical operator

   AND (&&) combines conditions that both must be true; OR (||) would allow values outside the range.

3. Step 3: Check inclusivity

   Using >= and <= includes 50 and 100 themselves.

4. Final Answer:

   score >= 50 && score <= 100 -> Option C

5. Quick Check:

   Between means AND, not OR [OK]

Hint: Use && to combine conditions that both must be true [OK]

Common Mistakes:

• Using || which allows values outside range
• Using > and < excludes boundary values
• Confusing AND and OR logic