import type { ListOf } from '../internal/types/union.js';
export type Mean<AS extends readonly unknown[]> = AS extends [] | readonly []
  ? 0
  : HasOnlyNumberOrBigInt<ListOf<AS[number]>> extends true
  ? AS[number] extends number | bigint
    ? GeneralizeNumeric<AS[number]>
    : never
  : never;
type HasOnlyNumberOrBigInt<AS extends readonly unknown[]> = [
  HasOnlyNumberAndHaltAtNonNumeric<AS>,
  HasOnlyBigIntAndHaltAtNonNumeric<AS>,
] extends [true, false]
  ? true
  : [
      HasOnlyNumberAndHaltAtNonNumeric<AS>,
      HasOnlyBigIntAndHaltAtNonNumeric<AS>,
    ] extends [false, true]
  ? true
  : false;
type HasOnlyNumberAndHaltAtNonNumeric<AS extends readonly unknown[]> =
  AS extends readonly [infer THead, ...infer TTail]
    ? TTail extends []
      ? THead extends number
        ? true
        : false
      : THead extends number
      ? HasOnlyNumberAndHaltAtNonNumeric<TTail> extends true
        ? true
        : false
      : false
    : never;
type HasOnlyBigIntAndHaltAtNonNumeric<AS extends readonly unknown[]> =
  AS extends readonly [infer THead, ...infer TTail]
    ? TTail extends []
      ? THead extends bigint
        ? true
        : false
      : THead extends bigint
      ? HasOnlyBigIntAndHaltAtNonNumeric<TTail> extends true
        ? true
        : false
      : false
    : never;
type GeneralizeNumeric<N extends number | bigint> = number extends N
  ? N
  : bigint extends N
  ? N
  : N extends number
  ? number
  : bigint;
/**
 * Returns the mean of all elements in the array (only for number or bigint arrays).
 *
 * **Do not** use it with an array of bigint with zero elements, as it will return `0` instead of `0n`.
 * @param array The array to get the mean of.
 *
 * @throws {TypeError} If the array contains non-numbers or mixed numbers and bigints.
 *
 * @example
 * ```typescript
 * const arr = [2, 1, 3.5, 3, 4];
 * mean(array); // => 2.7
 * ```
 */
declare const mean: <T>(
  array: T[] | readonly T[],
) =>
  | (HasOnlyNumberOrBigInt<ListOf<T>> extends true
      ? T extends number | bigint
        ? GeneralizeNumeric<T>
        : never
      : never)
  | (HasOnlyNumberOrBigInt<ListOf<T>> extends true
      ? T extends number | bigint
        ? GeneralizeNumeric<T>
        : never
      : never);
export default mean;
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