Logical operators in Swift - Step-by-Step Execution

Concept Flow - Logical operators

Start

↓

Evaluate Left Operand

↓

Evaluate Right Operand

↓

Apply Logical Operator

↓

Result: true or false

↓

Use Result in Condition or Expression

↓

End

Logical operators take two true/false values and combine them to produce a new true/false result used in decisions.

Execution Sample

Swift

let a = true
let b = false
let result = a && b
print(result)

This code checks if both a and b are true using AND (&&) and prints the result.

Execution Table

Step	Expression	Left Operand	Right Operand	Operator	Result	Explanation
1	a	true	-	-	true	Variable a is true
2	b	-	false	-	false	Variable b is false
3	a && b	true	false	&&	false	AND requires both true, b is false so result is false
4	print(result)	-	-	-	false	Output is false

💡 Finished evaluating logical AND; result is false because one operand is false

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
a	undefined	true	true	true	true
b	undefined	undefined	false	false	false
result	undefined	undefined	undefined	false	false

Key Moments - 2 Insights

Why is the result false even though one operand is true?

Because the AND operator (&&) needs both operands to be true. The execution_table row 3 shows left is true but right is false, so result is false.

What happens if we use OR (||) instead of AND (&&)?

OR returns true if at least one operand is true. So if we change operator in row 3 to ||, result would be true because a is true.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the result of 'a && b'?

A true

B false

C undefined

D error

💡 Hint

Check the 'Result' column in row 3 of the execution_table.

At which step is variable b assigned its value?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Expression' and 'Right Operand' columns in execution_table row 2.

If we change the operator in step 3 from && to ||, what would be the new result?

A true

B false

C undefined

D error

💡 Hint

Recall that OR (||) returns true if either operand is true; see variable values in variable_tracker.

Concept Snapshot

Logical operators combine two Boolean values.
Common operators: && (AND), || (OR), ! (NOT).
AND returns true only if both are true.
OR returns true if at least one is true.
NOT reverses true/false.
Used in conditions to control program flow.

Full Transcript

This visual execution shows how logical operators work in Swift. We start with two variables a and b, assigned true and false. Then we evaluate the expression a && b. The AND operator requires both sides to be true, but since b is false, the result is false. Finally, we print the result which outputs false. The variable tracker shows how a, b, and result change step by step. Key moments clarify why the result is false and what would happen if we used OR instead. The quiz tests understanding of the steps and operator behavior.