/**
 * Iterate over each item in `a` with `fn(a[i], i)`.
 */
export declare function each<I>(a:readonly I[], fn:each_fn_T<I>):I[]
export declare function maybe_each<I, Or = null>(
	maybe_a:readonly I[]|undefined,
	fn:each_fn_T<I>,
	or?:Or
):I[]|Or
export declare type each_fn_T<I> = (val:I, idx:number)=>void