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Ownership & Borrowing

RGC uses an ownership model to manage memory: every value has a unique owner and is freed when it goes out of scope; borrowing (@ / @var) provides safe shared access. No GC, no runtime overhead.

Ownership​

After a value is moved, the original variable can no longer be used:

def main() {
    a = "hello"
    b = a        # ownership moves from a to b
    print(b)     # ok
    # print(a)   # error: a has been moved
}

Read-only borrowing @​

Use @ to borrow a value without transferring ownership:

def length(s: @str) -> int {
    return s.len()
}

def main() {
    text = "RGC"
    print(length(@text))   # read-only borrow
    print(text)            # text is still usable
}

Mutable borrowing @var​

Use @var when you need to modify a value:

def push_zero(lst: @var List[int]) {
    lst.push(0)
}

Method calls​

Container methods handle borrowing automatically:

def main() {
    list = [1, 2, 3]
    list.push(4)   # mutable borrow
    n = list.len() # read-only borrow
}

Memory safety guarantees​

Ownership and borrow checking happen at compile time:

  • No use-after-move
  • No dangling references
  • No data races (mutable and shared borrows are exclusive)
  • No GC pauses; predictable performance

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