import type { Digit } from "..";
import type { Args, Fn } from "../HKT";
import type { AssertBool } from "../helpers";

/**
 * Check if a number is a {@link Digit}.
 *
 * Sig: `(n: number) => boolean`
 */
export type IsDigit<N extends number> = AssertBool<
  number extends N ? boolean
  : N extends Digit ? true
  : false
>;

/**
 * [Fn] Check if a number is a {@link Digit}.
 *
 * Sig: `(n: number) => boolean`
 */
export default interface IsDigitFn extends Fn<[number], boolean> {
  def: ([n]: Args<this>) => IsDigit<typeof n>;
}