216 - Slice (multiple helper method, but straightforward)

[code-brewer]

Though contain many helper method, but it is very straightforward. All test case passed.

type NumberToArray<T extends number, S extends unknown[] = []> = S['length'] extends T ? S : NumberToArray<T, [...S, 1]>

//  A.len > B.len
type _MinusAB<A extends any[], B extends any[], R extends any[] = []> = 
    A["length"] extends B["length"] ? R["length"] : _MinusAB<A, [1, ...B], [1, ...R]>

// return converted/normalized/positive index pos：
type NormalizeIndex<A extends any[], N extends number, Ng=`${N}`> = Ng extends `-${infer E extends number}` 
    ? _MinusAB<A, NumberToArray<E>> 
    : N

type getHead<A, N, R extends any[] = []> = A extends [infer F, ... infer Tail] 
  ? R['length'] extends N ? R : getHead<Tail, N, [ ...R, F]> 
  : R

type getTail<A extends any[], N, Pop extends any[] = [], Tail extends any[] = A> = Pop['length'] extends N  
  ? Tail 
  : A extends [infer F, ... infer Tail] 
    ? getTail<Tail, N, [... Pop, F], Tail>
    : []

type Slice<Arr extends any[], Start extends number=0, End extends number= Arr["length"]> 
  = getTail<getHead<Arr, NormalizeIndex<Arr, End>>, NormalizeIndex<Arr, Start>>