flan/examples/core-input-keys.flan
Joseph Ferano 26c53e0a19 Every defn in the tree states its return type, and Unit is written ()
The mechanical half, ahead of the parser change that needs it. tools/unit-return.py
fills the empty slot with () and rewrites Unit as () wherever a type is spelled --
(Fn [i32] Unit), (Map i32 Unit), a return type written out.

Deciding whether a defn already had a return type is the whole difficulty, and
the script does it the way parse.ml did: is_type_form is transcribed rather than
improved, because being identical to the parser it replaces is what makes the
sweep meaning-preserving. It is re-runnable, so the lanes that branched before
this can have the same pass at merge:

    python3 tools/unit-return.py .
    python3 tools/unit-return.py --in-strings test/test_flan.ml test/test_acceptance.ml \
        test/test_session.ml emacs/test-flan-dev.el emacs/test-flan-mode.el
    python3 tools/unit-return.py --raw-ml lib/prelude.ml
    python3 tools/unit-return.py --in-html web/index.html

-v logs every defn it saw and what it decided, which is how a sweep of 440 sites
gets reviewed at all. Embedded modes pool a file's type declarations across all
its fragments, because a snippet split across concatenation -- decls ^ "(defn f
[s [u8]] Cursor ...)" -- cannot see the names the other half declared; pooled
names count only in bare-symbol position, for the same reason the prelude's do.
A fragment that cuts off mid-form is skipped rather than guessed at. Five sites
in test_flan.ml still needed a hand, and they are in this commit.

Two things ride along because the sweep needs them: parse.ml reads a lone () as
the return type of a function with no body, which was not a shape the old
optional slot could produce; and the map refusals name () rather than Unit, since
that is now the spelling a caller wrote.
2026-09-12 23:06:40 +07:00

48 lines
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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 `defvar` 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)
(defvar 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? :right) (set (.x ball) (+ (.x ball) 2.0)))
(when (rl/key-down? :left) (set (.x ball) (- (.x ball) 2.0)))
(when (rl/key-down? :up) (set (.y ball) (- (.y ball) 2.0)))
(when (rl/key-down? :down) (set (.y ball) (+ (.y ball) 2.0)))
;; Draw
(rl/begin-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)
(rl/end-drawing)))