Functions

Function Definition

def greet():
    """Greet all players"""
    /tellraw @a {"text":"Hello!", "color":"green"}

Functions with Parameters

Cobble supports function parameters using Minecraft’s macro system:

def give_reward(player, amount):
    """Give a reward to a player"""
    /give {player} minecraft:diamond {amount}
    /tellraw {player} {"text":"You received diamonds!", "color":"gold"}

Use {param_name} in Cobble source. Cobble compiles it to Minecraft’s $(param_name) macro syntax, so the line becomes a macro line in the generated function. Text outside the braces, such as minecraft:diamond, stays literal.

Parameter names must be unique. Default parameter values, *args, and **kwargs are not supported.

Calling Functions

def main():
    greet()
    give_reward("Steve", 5)

Functions can return integer scoreboard values:

def double(value):
    return value * 2

def main():
    score = double(5) + 1

Cobble compiles return expr to Minecraft’s function return value. Calls used inside expressions are executed with execute store result score ... run function ..., so returned values are scoreboard integers. Integer-returning user functions can be used in assignments, arithmetic expressions, and conditions such as if ready(): or while should_continue():. Imported functions have the same return metadata after their module is processed. Use storage or explicit output variables for non-integer data.

Recursion is not supported. A function may not call itself, directly or through a cycle of other functions. Recursive calls are rejected at compile time with an error such as Recursive call to 'fact' is not supported. Rewrite the recursion as a loop (while/for) instead. Rewrite recursion as a while or for loop with explicit state.

Parameterized functions can call other parameterized functions and forward their own parameters:

def give_reward(player, item, count):
    /give {player} minecraft:{item} {count}

def reward_nearby(player, item, count):
    give_reward(player, item, count)
    /tag {player} add rewarded