Syntax And Types

Blocks And Comments

Cobble uses indentation-based blocks after : and needs no braces or semicolons. Unexpected indentation and dedents that do not match a previous block level are reported as diagnostics before parsing. Lines starting with / are Minecraft commands; see Minecraft Commands.

# A comment runs to the end of the line.

def my_function():
    """
    A docstring describes the function.
    It can span multiple lines.
    """
    /say Hello, world!

Data Types

Numbers

score = 10
health = 100

Numbers are internally stored as Minecraft scoreboard values.

Strings

message = "Hello, world!"

Booleans

is_active = True
is_disabled = False

Booleans are stored as integers in Minecraft scoreboards (0 for False, 1 for True).

Lists, Maps, and None

from stdlib import datapack

items = ["minecraft:diamond", "minecraft:emerald"]
config = {"chance": 1, "note": "missing"}
first_item = items[0]
chance = config.chance

datapack.predicate("maybe", {
    "type": "minecraft:random_chance",
    "chance": 1,
    "comment": None
})

Lists and maps are storage-backed values. Cobble supports attribute and subscript access when the base value resolves to a storage path, including literal or constant subscript segments, runtime integer list/string indexes, and runtime string map keys. Arbitrary Python-style indexing is not a general runtime feature yet.

len(value) returns the length of literal arrays, maps, and strings, as well as storage-backed list, map, and string values. Storage-backed lengths compile to a Minecraft data get storage ... result stored in a scoreboard integer.

None is supported where Cobble serializes data pack JSON resources and is emitted as JSON null. It has no scoreboard value, so keep it out of numeric and boolean expressions. Minecraft NBT/SNBT storage has no null type, so storage literals reject None; use an explicit sentinel value for storage.

Type System

A variable’s type is inferred from its first assignment and stays fixed after that:

x = 5        # integer
y = True     # boolean
name = "Bob" # string

x = 20       # OK: still an integer
x = True     # error: x is an integer

Assigning a value of another type is a type-mismatch error:

Error: type-mismatch: Type mismatch for variable 'x'.
   ╭─[ main.cbl:6:1 ]
   │
 6 │ x = True
   │ ┬
   │ ╰── Type mismatch for variable 'x'.
   │
   │ Note: Variable was previously defined as type: integer
   │       Cannot reassign to type: boolean
   │       Use a different variable name or keep all assignments to 'x' the same type.
───╯

Numeric Range And Precision

Numbers are scoreboard integers, so they range from -2147483648 to 2147483647. A float literal is truncated to an integer and a literal outside the range is clamped, each with a warning:

pi = 3.14159       # warning: truncated to 3
huge = 9999999999  # warning: clamped to 2147483647

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