Ownership by example

The compiler borrows a value while a call reads it and counts it when it escapes. Calling size does not prevent the caller from using the string again. Save this example and run fibc explain FILE to inspect ownership decisions. Cell supplies local mutation and & passes a cell in-out; cells cannot cross threads. The ownership guide includes a checked rejection. Next: a project.

(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