Chapter 4b - Functions

Why functions

A function packages a piece of work behind a name. Game code calls the same ideas often — damage, healing, formatting a HUD line — so you write them once and reuse them.

func double(n: int) -> int:
    return n * 2

print(double(7))  # 14

🧪 Try it

Anatomy

func name(param: Type) -> ReturnType:
    # body
    return value

Piece	Role
func	Starts a function
parameters	Inputs the caller passes in
-> Type	Optional return type (recommended in lessons)
return	Sends a result back to the caller

Call a function with parentheses: double(7). Without (), you only mention the function — you do not run it.

Mini quiz — functions

Quiz

Functions

1 / 3

What does return do?

Pick an answer to see if you are right.

Multiple parameters and defaults

Pass several values, separated by commas. Default arguments fill in when the caller omits them.

func heal(hp: int, amount: int = 5, max_hp: int = 100) -> int:
    return mini(max_hp, hp + amount)

print(heal(90))        # 95 — amount defaults to 5
print(heal(90, 20))    # 100 — capped by max_hp

🧪 Try defaults

Functions calling functions

Small helpers compose. Keep each function focused — one job is easier to test.

func armor_block(dmg: int, armor: int) -> int:
    return maxi(0, dmg - armor)

func apply_hit(hp: int, dmg: int, armor: int) -> int:
    return maxi(0, hp - armor_block(dmg, armor))

🧪 Try composition

Challenge: apply hit

Write apply_hit(hp, dmg, armor) so it:

1. Reduces damage by armor (damage cannot go below 0)
2. Subtracts that from hp (hp cannot go below 0)
3. Returns the new HP

Example: hp=20, dmg=8, armor=3 → blocked damage is 5 → result 15.

Indentation

Indent with 4 spaces. Click Reset if an old draft looks flat.

Exercises

Warm up with a pure return, format a status string, then clamp a value into a range.

Activity: Triple

Write triple(n) so it returns n * 3.

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