Chapter 05: Logic

Code that runs in a straight line is boring. Smart programs make decisions.

5.1 The Judge (Comparison Operators)

Before we make a decision, we need to judge the situation. The result is always a Boolean (true / false).

Operator	Meaning	Example	Result
==	Equal to	5 == 5	true
!=	Not Equal	5 != 3	true
<	Less than	10 < 5	false
>=	Greater or Equal	10 >= 10	true

5.2 The Circuit (Boolean Algebra)

Sometimes you need to check multiple things.

AND (&&)

Both must be true.

"I will buy the car if it is Red AND Fast."

• true && true $\rightarrow$ true
• true && false $\rightarrow$ false

OR (||)

at least One must be true.

"I will eat if I am Hungry OR Bored."

• true || false $\rightarrow$ true
• false || false $\rightarrow$ false

NOT (!)

Flip the result.

• !true $\rightarrow$ false

5.3 The Fork (If / Else)

We use if to control the flow.

isOpen := true
isHoliday := false

if !isOpen {
    // Stop here if closed
    fmt.Println("Come back tommorow.")
} else if isHoliday {
    // Open, but holiday
    fmt.Println("Holiday hours.")
} else {
    // Normal flow
    fmt.Println("Welcome!")
}

5.4 The Switch (Cleaner Logic)

If you have many conditions, if/else gets messy. Use switch.

role := "admin"

switch role {
case "admin":
    fmt.Println("Full Access")
case "user":
    fmt.Println("Limited Access")
default:
    fmt.Println("Access Denied")
}

Think of it as a railway switchyard, directing the train to the correct track.

🎓 Knowledge Check

1. Does Go use parentheses () for if conditions? No. We write if x > 10 { }.
2. What happens if you declare a variable inside an if statement? It is only visible inside that if block (Scope).
3. Does Go have a while loop? No. Go only has for. We use for condition { } to mimic while.