Logic and Variables

This page covers how to make decisions, store information, and repeat things in Carbon Lang.

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Variables

A variable is a named box that holds a value. You create one by just writing its name, an equals sign, and a value.

@ Creating variables
count = 0
range = 10
speed = 1.5
target = nearest_entity
message = "Hello!"

No special keywords needed. Just write it.

You can change a variable the same way:

count = count + 1
speed = speed * 2

Types — Invisible to You

You never need to write a type. Carbon figures it out automatically:

What you write	What Carbon sees
count = 10	count is a whole number
speed = 1.5	speed is a decimal number
name = "ruby"	name is text
target = nearest_entity	target is an entity

Persistent Data

Normal variables reset when the script ends. If you want data to stick around, use a prefix:

Prefix	What it saves
#p.	Saved per player
#a.	Applies to all players at once
#e.	Saved per entity
#b.	Saved per block
#w.	Saved for the whole world
#mod.	Saved globally for your mod

@ Count how many times this player has right-clicked
#p.clicks = #p.clicks + 1

@ Track a world-wide boss kill counter
#w.boss_kills = #w.boss_kills + 1

@ Give all players a score
#a.score += 10

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If Statements

An if checks whether something is true. If it is, the code inside runs.

if (holding)
run (scripts/glow_effect.cj)

If not true, it skips to else (if you have one):

if (holding)
run (scripts/glow_effect.cj)
else
run (scripts/normal.cj)

And — anif

Because Carbon Lang doesn't use indentation for logic, "and" is written as anif on the next line:

if (holding)
anif (sneaking)
run (scripts/special_ability.cj)

This only runs if the player is BOTH holding the item AND sneaking.

Or

Use or on the same line as if:

if (holding) or (sneaking)
run (scripts/glow.cj)

This runs if the player is holding OR sneaking.

Not

Use not to check the opposite:

if not (crouching)
run (scripts/fly.cj)

You can combine anif not:

if (holding)
anif not (sneaking)
run (scripts/run_fast.cj)

Math in Conditions

You can use math inside conditions:

if (health < max_health / 2)
run (scripts/low_health_warning.cj)

if (distance #s target < range)
run (scripts/attack.cj, target)

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Loops

A loop repeats something a set number of times:

loop (5)
run (scripts/spawn_enemy.cj)
end

A loop with no number runs every game tick (20 times per second):

loop
if (#p.is_flying)
run (scripts/flight_particle.cj)
end

Stopping a Loop Early

Use stop to exit a loop before it finishes:

loop (100)
run (scripts/spawn.cj)
if (count > 10)
stop
end

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Running Scripts

Use run to call another script:

run (scripts/fireball.cj)

Passing Values Into a Script

You can send variables along with the script:

run (scripts/wave_spawner.cj, mob_type)

In wave_spawner.cj, you receive it at the top:

carbonjava

input (mob_type : string)

@ Now you can use mob_type in this script
add mob
name (wave_enemy)
copy (mob_type)
health (20)
end

Running Two Scripts at the Same Time

run (scripts/explosion.cj) and (scripts/sound.cj)   @ These fire together
run (scripts/cleanup.cj)                              @ This fires after both finish

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Full Example

carbonjava

@ Track clicks and give an effect every 10 clicks

#p.clicks = #p.clicks + 1

if (#p.clicks >= 10)
run (scripts/reward_effect.cj)
#p.clicks = 0          @ Reset the counter

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Writing to Another Player's Data

To write persistent data to a specific player who isn't the current player, use #player(variable).field:

@ Store the sender's name in the target player's data
#player(target).tpa_requester = #p.name

target must be a variable holding a player/entity.

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Built-in Read-Only Properties

These are built into Carbon — you can read them but cannot assign to them.

On the current player (#p.):

name = #p.name           @ username
hp = #p.health           @ current health
level = #p.xp_level      @ XP level
mode = #p.gamemode       @ survival, creative, etc.

On self/mob (#s.):

hp = #s.health
pos = #s.position

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Exiting a Script Early

Use exit to stop a script immediately:

if (#p.tpa_requester == "null")
run (scripts/no_request.cj)
exit

@ This only runs if the condition above was false
requester = find_player (#p.tpa_requester)

exit stops the whole script. stop only exits a loop.

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Finding a Player by Name

Use find_player to look up an online player from a stored name:

requester = find_player (#p.tpa_requester)

if (requester == null)
run (scripts/player_offline.cj)
exit

Returns null if the player is not online. Always check for null before using the result.