Logical operators (&&, ||, !) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of combined logical operators

What is the output of this Ruby code?

Ruby

a = true
b = false
puts (a && !b) || (b && !a)

A true

B SyntaxError

C nil

D false

💡 Hint

Remember that ! reverses the boolean value and && has higher precedence than ||.

a is true, b is false. !b is true, so (a && !b) is true. (b && !a) is false. true || false is true.

❓ Predict Output

intermediate

Result of negation and OR

What will this Ruby code print?

Ruby

x = false
puts !x || x

A nil

B false

C true

D RuntimeError

💡 Hint

Check what !x evaluates to when x is false.

!x is true because x is false. true || false is true.

❓ Predict Output

advanced

Complex logical expression output

What is the output of this Ruby code snippet?

Ruby

a = true
b = false
c = true
puts a && b || !c && a

A true

B false

C nil

D SyntaxError

💡 Hint

Remember operator precedence: && before ||, and ! before both.

a && b is false (true && false). !c is false (!true). So false || false && true is false || (false && true) = false || false = false.

❓ Predict Output

advanced

Output of negation with multiple operators

What does this Ruby code print?

Ruby

x = true
y = false
puts !(x || y) && (x && !y)

A false

B true

C TypeError

D nil

💡 Hint

Evaluate inside parentheses first, then apply negation and AND.

x || y is true, so !(x || y) is false. x && !y is true && true = true. false && true is false.

🧠 Conceptual

expert

Understanding short-circuit evaluation

In Ruby, which statement about the expression `false && (some_method)` is true?

A some_method is called only if it returns false

B some_method is called only if it returns true

C some_method is always called because && evaluates both sides

D some_method is never called because false && anything is false

💡 Hint

Think about how Ruby stops evaluating && when the first value is false.

Ruby uses short-circuit evaluation: if the first value in && is false, it does not evaluate the second.