Ownership and borrowing

Values are borrowed for reads and retained when stored, returned or captured by an escaping closure. The compiler chooses scope allocation and counting. Closures that stay within a call can borrow; escaping closures keep their data alive. Private cells mutate locally; atoms synchronize shared updates. freeze marks a shareable object graph frozen and weak avoids retaining a referent. Cycles of strong references can leak; use a weak link where appropriate.

&x is an in-out place, not a second first-class reference. Passing the same place to two in-out parameters in one call is rejected. Save the accepted example for fibc explain FILE. Full rules: ownership, types, and the checked Appendix A cases in syntax.

(ns main)
(defun size (s: str) -> i64 (str-len s))
(defun main () -> i64
  (let ((s "hello") (n (size s))) (do (println n) (println s) 0)))

5
hello
0

(defun bar (&a &b) (append &a 1) (append &b 2))
(defun main () -> i64
  (let ((x (cell [3 4]))) (do (bar &x &x) 0)))