flan/test/programs/values.flan
Joseph Ferano a4c6b996ff def re-runs its initialiser, and defvar is renamed defonce
The trio the author decided on 2026-09-20 is now all built: def is CL's
defparameter — its initialiser runs on every daemon re-run, unguarded, so
an edited initialiser repaints the same storage on C-c C-c plus re-run —
defonce (Clojure's name for CL's defvar, per the author) initialises once
behind the .init~once. flag, and defconst stays the image.

One parse arm reads both forms; the difference is Ast.reinit, carried to
Tast.global's grerun. Emit.startup_plan gives a def no guard flag, and
Check.check_global lifts every def initialiser — zero and literal
included — into global/<n>, so the host's startup reaches it through the
function cell and a re-evaluated def swaps it (Session's def_inits;
Emit.redefinition declares the cell for a non-sibling target). The old
defvar spelling is refused with the rename and both compiling spellings,
and every program, test, doc and editor list is swept — except sand.flan,
the author's live WIP, whose seven defvar lines are flagged in FIX.org
and keep its three dependent tests red on this branch.
2026-09-21 07:12:04 +07:00

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;;;; Value semantics, spec-memory.md. Not covered by calc-me, and the property
;;;; most likely to be silently wrong in a backend: a struct or a fixed array
;;;; copies on assignment, a slice copies only its view.
(defstruct P [x i32])
(defonce arr [3 i32])
(defn main [] i32
(let [a (P {.x 1})]
(let [b a] ; a copy, not an alias
(set (.x a) 99)
(print (.x b)) (println ""))) ; 1
(set (at arr 0) 5)
(let [c arr] ; fixed arrays are values too
(set (at arr 0) 77)
(print (at c 0)) (println "")) ; 5
(let [s (bytes-view "hello")]
(let [v (slice s 1 3)] ; a view into the same bytes
(print v) (println ""))) ; el
0)