flan/examples/core-input-keys.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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;;;; raylib [core] example - input keys
;;;;
;;;; examples/core/core_input_keys.c. Faithful, and the only thing worth noting
;;;; is a Flan rule rather than a raylib one.
;;;;
;;;; The C moves the ball by writing `ballPosition.x += 2.0f` on a local
;;;; struct. Flan has the same thing — a local IS an assignable place
;;;; (spec-memory.md) — but the local has to be a `defonce` here rather than a
;;;; `let` inside the loop, because a `let` binding is rebound every iteration
;;;; and the position has to survive between frames. The C's variable is
;;;; outside its while loop for the same reason; this is that, spelled with the
;;;; storage the language has.
;;;;
;;;; `(set (.x ball) ...)` works on a struct field of a global: a field of an
;;;; assignable place is itself one.
(import rl "vendor:raylib")
(defconst screen-width 800)
(defconst screen-height 450)
(defonce ball rl/Vector2)
(defn main [] ()
(rl/init-window screen-width screen-height
"raylib [core] example - input keys")
(defer (rl/close-window))
(set ball (rl/Vector2 {.x (f32 (/ screen-width 2))
.y (f32 (/ screen-height 2))}))
(rl/set-target-fps 60)
(until (rl/window-should-close?)
;; Update. key-down? and not key-pressed?: this is meant to repeat for as
;; long as the key is held, which is the whole difference between the two.
(when (rl/key-down? :key-right) (set (.x ball) (+ (.x ball) 2.0)))
(when (rl/key-down? :key-left) (set (.x ball) (- (.x ball) 2.0)))
(when (rl/key-down? :key-up) (set (.y ball) (- (.y ball) 2.0)))
(when (rl/key-down? :key-down) (set (.y ball) (+ (.y ball) 2.0)))
;; Draw
(rl/with-drawing
(rl/clear-background rl/raywhite)
(rl/draw-text "move the ball with arrow keys" 10 10 20 rl/darkgray)
(rl/draw-circle-v ball 50.0 rl/maroon))))