flan/examples/core-input-multitouch.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

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;;;; raylib [core] example - input multitouch
;;;;
;;;; examples/core/core_input_multitouch.c. No new bindings: the whole touch
;;;; surface was already there for sand.flan's read-out.
;;;;
;;;; The C keeps `Vector2 touchPositions[MAX_TOUCH_POINTS]`, and this is the
;;;; first example that needs a fixed array whose element type is a STRUCT
;;;; rather than a number. That works — `[10 rl/Vector2]` is ten Vector2s laid
;;;; out flat, no headers, and `(at touch-positions i)` is a place that can be
;;;; assigned a whole struct. Nothing in the repository used one before, so it
;;;; is worth saying that it does.
;;;;
;;;; It is a top-level `defvar` and not a local, which is NOT a stylistic
;;;; choice. A `let` binding takes no type annotation, so the only way to make
;;;; a fixed array inside a function is to initialise it from a literal with
;;;; every element written out — ten `(rl/Vector2 {.x 0.0 .y 0.0})`s here, and
;;;; thirty-two in the gestures testbed. A zeroed local array of a given type
;;;; cannot be spelled. Static storage is what the C's `= { 0 }` gets anyway.
;;;;
;;;; On a desktop with no touchscreen get-touch-point-count is 0 and this draws
;;;; nothing at all, which is correct and is also what the C does. The window
;;;; opening and the help text appearing is the whole of what can be checked
;;;; without hardware.
(import rl "vendor:raylib")
(defconst screen-width 800)
(defconst screen-height 450)
(defconst max-touch-points 10)
(defvar touch-positions [max-touch-points rl/Vector2])
(defn main [] ()
(rl/init-window screen-width screen-height
"raylib [core] example - input multitouch")
(defer (rl/close-window))
(rl/set-target-fps 60)
(until (rl/window-should-close?)
;; Update
(let [count (min max-touch-points (rl/get-touch-point-count))]
(dotimes [i count]
(set (at touch-positions i) (rl/get-touch-position i)))
;; Draw
(rl/begin-drawing)
(rl/clear-background rl/raywhite)
(dotimes [i count]
(let [p (at touch-positions i)]
;; raylib reports (0,0) for a slot that is not being touched, so the
;; C filters on it and so does this. It means a real touch in the
;; very top-left corner is dropped; that is raylib's ambiguity, not
;; something the port introduced.
(when (and (> (.x p) 0.0) (> (.y p) 0.0))
(rl/draw-circle-v p 34.0 rl/orange)
;; The C's TextFormat("%d", i). This used to need examples/digits.flan
;; and a table of one-character strings; (string b) makes the
;; number a string with no instructions, so it is one draw-text and
;; this file imports nothing but raylib.
(rl/draw-text (string (i64->bytes (i64 i)))
(- (i32 (.x p)) 10) (- (i32 (.y p)) 70) 40
rl/black))))
(rl/draw-text "touch the screen at multiple locations to get multiple balls"
10 10 20 rl/darkgray)
(rl/end-drawing))))