import type { Vec2, Vec2Like } from './types';
/** Create a Vec2 (zero vector by default). */
export declare function create(x?: number, y?: number): Vec2;
/** Allocate a new Vec2 copy. Difference from copy: clone allocates, copy writes into an existing out. */
export declare function clone(a: Vec2Like): Vec2;
/** out = a. Returns out. aliasing-safe (copy(v, v) is a no-op). */
export declare function copy(out: Vec2, a: Vec2Like): Vec2;
/** Write the components and return out. */
export declare function set(out: Vec2, x: number, y: number): Vec2;
/**
 * Approximate equality: every component differs by ≤ epsilon. NaN inputs always return false (matches IEEE 754).
 */
export declare function equals(a: Vec2Like, b: Vec2Like, epsilon?: number): boolean;
/** out = a + b. aliasing-safe. */
export declare function add(out: Vec2, a: Vec2Like, b: Vec2Like): Vec2;
/** out = a - b. aliasing-safe. */
export declare function sub(out: Vec2, a: Vec2Like, b: Vec2Like): Vec2;
/** out = a * s. */
export declare function scale(out: Vec2, a: Vec2Like, s: number): Vec2;
/** out = -a. The `0 - x` form avoids -0 (test toBe(0) uses Object.is and distinguishes ±0). */
export declare function negate(out: Vec2, a: Vec2Like): Vec2;
/** Dot product a · b. */
export declare function dot(a: Vec2Like, b: Vec2Like): number;
/** Squared length |a|² (avoids sqrt overhead; useful on hot paths comparing distances). */
export declare function lengthSq(a: Vec2Like): number;
/** Euclidean length |a|. */
export declare function length(a: Vec2Like): number;
/** Distance between two points |a - b|. */
export declare function distance(a: Vec2Like, b: Vec2Like): number;
/**
 * out = a / |a| (unit-length).
 *
 * @degrade Zero vector (|a|² < EPS_NORMALIZE) silently falls back to the zero vector;
 * no NaN, no throw (gl-matrix style, AC-06 / D-P12).
 * @degrade NaN inputs → NaN outputs: when a component is NaN, lenSq=NaN; the `lenSq < EPS`
 * branch is false → goes through 1/sqrt(NaN)=NaN → output is all NaN (IEEE-754 NaN propagation;
 * still does not throw).
 *
 * @example
 * ```ts
 * vec2.normalize(out, [3, 4]);     // → (0.6, 0.8)
 * vec2.normalize(out, [0, 0]);     // → (0, 0) zero vector falls back (no NaN; AC-06 no throw)
 * vec2.normalize(out, [NaN, 1]);   // → (NaN, NaN) IEEE-754 propagation
 * ```
 */
export declare function normalize(out: Vec2, a: Vec2Like): Vec2;
/** out = lerp(a, b, t). t is not clamped (extrapolation semantics matches glam / wgpu-matrix). aliasing-safe. */
export declare function lerp(out: Vec2, a: Vec2Like, b: Vec2Like, t: number): Vec2;
/**
 * out = frame-rate-INDEPENDENT exponential smoothing of `current` toward `target`:
 * `lerp(current, target, 1 − exp(−decayRate · dt))`. Semantics match Bevy
 * `StableInterpolate::smooth_nudge` / three.js `MathUtils.damp` (1st-order decay, NOT Unity
 * `SmoothDamp`'s 2nd-order spring). `dt=0` → out=current; large `decayRate·dt` → out≈target.
 * Frame-rate independent by construction (one `dt` step = two composed `dt/2` steps). aliasing-safe.
 * See vec3.smoothDamp for the full contract. */
export declare function smoothDamp(out: Vec2, current: Vec2Like, target: Vec2Like, decayRate: number, dt: number): Vec2;
/**
 * out = Catmull-Rom spline point on the segment between `p1` and `p2`, with `p0` / `p3` the
 * neighbor control points setting the endpoint tangents (tension 0.5 — the Bevy
 * `CubicCardinalSpline::new_catmull_rom` / three.js default). Interpolates the control points
 * (`t=0` → `p1`, `t=1` → `p2`). See vec3.catmullRom for the full contract + whole-polyline
 * sampling. aliasing-safe. */
export declare function catmullRom(out: Vec2, p0: Vec2Like, p1: Vec2Like, p2: Vec2Like, p3: Vec2Like, t: number): Vec2;
/** Component-wise min. */
export declare function min(out: Vec2, a: Vec2Like, b: Vec2Like): Vec2;
/** Component-wise max. */
export declare function max(out: Vec2, a: Vec2Like, b: Vec2Like): Vec2;
/**
 * out = perp(a) — 2D counter-clockwise 90° rotation: (x, y) → (-y, x).
 *
 * Derives from cross(a, b) reducing to a scalar determinant in 2D; this API serves hot paths
 * (collision / normals).
 * aliasing-safe: reads a's components into locals before writing out.
 */
export declare function perp(out: Vec2, a: Vec2Like): Vec2;
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