import type { Vec4, Vec4Like } from './types';
/** Create a Vec4 (zero vector by default). */
export declare function create(x?: number, y?: number, z?: number, w?: number): Vec4;
/** Allocate a new Vec4 copy. */
export declare function clone(a: Vec4Like): Vec4;
/** out = a. aliasing-safe (copy(v, v) is a no-op). */
export declare function copy(out: Vec4, a: Vec4Like): Vec4;
/** Write the components and return out. */
export declare function set(out: Vec4, x: number, y: number, z: number, w: number): Vec4;
/**
 * Approximate equality: every component differs by ≤ epsilon. NaN inputs always return false (IEEE 754).
 */
export declare function equals(a: Vec4Like, b: Vec4Like, epsilon?: number): boolean;
/** out = a + b. aliasing-safe. */
export declare function add(out: Vec4, a: Vec4Like, b: Vec4Like): Vec4;
/** out = a - b. aliasing-safe. */
export declare function sub(out: Vec4, a: Vec4Like, b: Vec4Like): Vec4;
/** out = a * s. */
export declare function scale(out: Vec4, a: Vec4Like, s: number): Vec4;
/** out = -a. The `0 - x` form avoids -0. */
export declare function negate(out: Vec4, a: Vec4Like): Vec4;
/** Dot product a · b (4 components). */
export declare function dot(a: Vec4Like, b: Vec4Like): number;
/** Squared length |a|² (avoids sqrt overhead). */
export declare function lengthSq(a: Vec4Like): number;
/** Euclidean length |a|. */
export declare function length(a: Vec4Like): number;
/** Distance between two points |a - b|. */
export declare function distance(a: Vec4Like, b: Vec4Like): 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
 * vec4.normalize(out, [1, 2, 2, 0]);    // → (1/3, 2/3, 2/3, 0)
 * vec4.normalize(out, [0, 0, 0, 0]);    // → (0, 0, 0, 0) zero vector falls back (AC-06 no throw)
 * vec4.normalize(out, [NaN, 1, 0, 0]);  // → all NaN, IEEE-754 propagation
 * ```
 */
export declare function normalize(out: Vec4, a: Vec4Like): Vec4;
/** out = lerp(a, b, t). t is not clamped (extrapolation semantics). aliasing-safe. */
export declare function lerp(out: Vec4, a: Vec4Like, b: Vec4Like, t: number): Vec4;
/**
 * 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: Vec4, current: Vec4Like, target: Vec4Like, decayRate: number, dt: number): Vec4;
/** Component-wise min. */
export declare function min(out: Vec4, a: Vec4Like, b: Vec4Like): Vec4;
/** Component-wise max. */
export declare function max(out: Vec4, a: Vec4Like, b: Vec4Like): Vec4;
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