ludic/docs/language/input/input-bind.md
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feat(input): action maps + deterministic record/replay (#7)
The two ideas the input revamp leads with, built in Ludic over the
single-key poll every target already provides:

- Action maps: gameplay reads named actions, not physical keys, so keys
  are rebindable and a scheme is data. Input.bind(action, key),
  Input.down/pressed(action), Input.rebind(action, from, to).
- Deterministic record/replay: Input.poll() is the one per-frame input
  read; Input.record() captures the key each frame and Input.replay()
  feeds the tape back, so a run reproduces exactly — the seed of lockstep
  netcode. "Read input" and "read a recorded snapshot" are the same call.

runtime/native/input.ludic (spliced when the new Input.* methods are used;
pulls in core.ludic for rt_poll). emit_ns_call routes the methods to the
@fn_input_* runtime; parse.ludic gates the splice. Seven docs/language
pages; worked example + regression examples/library/input_actions.ludic
(1 0 1 1 0 1 0). Full suite 75 passed, self-host fixpoint intact, no golden
drift. The device layer (multi-key held, gamepads, touch, analog) needs a
platform key-state backend and is tracked separately.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-08-31 16:03:56 +03:00

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---
id: input-bind
name: Input.bind
category: input
kind: namespace-method
tokens: Input.bind
sig: Input.bind(action: str, key: int) -> void
tip: Bind a physical key to a named action, so gameplay reads the action, not the key.
order: 1
ns: Input
member: bind
---
Binds a physical key (a character code such as <code>'w'</code> or <code>' '</code>) to a named <em>action</em>, creating the action the first time it is named. Gameplay then reads the action with <a href="input-down.html"><code>Input.down</code></a> / <a href="input-pressed.html"><code>Input.pressed</code></a> instead of a raw key, which is what makes rebinding and alternate control schemes clean. Call it more than once with the same action to bind several keys to it; binding a key already on the action is a no-op. Actions are advanced once per frame by <a href="input-poll.html"><code>Input.poll</code></a>.
```ludic
program Bindings {
entry {
Input.bind("jump", ' ')
Input.bind("up", 'w')
Input.poll()
if Input.down("jump") { print(1) }
}
}
```