Cairo
Structs

Structs

With struct one can define arbitrary data types. They are implemented as a continuous list of felt values in memory.

Structs can be instantiated via the new keyword (note that new can't be used with let).

Members in structs can be accessed via the dot syntax (e.g. Foo.bar).

Struct pointers are implicitly casted to felt pointers (e.g. Foo* is casted to felt*).

Example

# A user-defined Struct called `Point`.
struct Point:
    member x : felt
    member y : felt
end

func get_origin() -> (origin : Point):
    let origin = Point(x=0, y=0)
    return (origin)
end

func main():
    alloc_locals

    # We can't use `let` to create a new `Point` with the `new` keyword...
    # let point_1 = new Point(x=1, y=2)

    # ...but `local` works...
    local point_1 : Point* = new Point(x=1, y=2)
    # ...and so does `tempvar`.
    tempvar point_2 : Point* = new Point(x=3, y=4)

    # To use `let` we can use the following syntax.
    let point_3 = Point(x=5, y=6)

    # Members in structs can be accessed via the `.` syntax.
    assert point_1.x = 1
    assert point_1.y = 2

    # Structs can also be received as return values from functions.
    let (origin) = get_origin()
    assert origin.x = 0
    assert origin.y = 0

    return ()
end