diff --git a/packages/ts-type-utils/src/index-of-tuple.d.mts b/packages/ts-type-utils/src/index-of-tuple.d.mts
index e0f55ccc32..0a67a04ebe 100644
--- a/packages/ts-type-utils/src/index-of-tuple.d.mts
+++ b/packages/ts-type-utils/src/index-of-tuple.d.mts
@@ -13,13 +13,11 @@ declare namespace TSTypeUtilsInternals {
       : number;
 }
 
-// type IndexOfTuple<T extends readonly unknown[]> = TypeEq<
-//   T,
-//   readonly []
-// > extends true
-//   ? never
-//   : TypeEq<T, []> extends true
-//   ? never
-//   : IsFixedLengthList<T> extends true
-//   ? Exclude<Partial<ListType.ButLast<T>>['length'], undefined>
-//   : SafeUint;
+// type IndexOfTuple<T extends readonly unknown[]> =
+//   TypeEq<T, readonly []> extends true
+//     ? never
+//     : TypeEq<T, []> extends true
+//       ? never
+//       : IsFixedLengthList<T> extends true
+//         ? Exclude<Partial<ListType.ButLast<T>>['length'], undefined>
+//         : SafeUint;
diff --git a/packages/ts-type-utils/src/index-type.d.mts b/packages/ts-type-utils/src/index-type.d.mts
index 7fdfc16cfa..c0e78dce44 100644
--- a/packages/ts-type-utils/src/index-type.d.mts
+++ b/packages/ts-type-utils/src/index-type.d.mts
@@ -1,7 +1,9 @@
 type Index<N extends number> = IndexOfTuple<MakeTuple<0, N>>;
 
+type IndexInclusive<N extends number> = IndexOfTuple<[...MakeTuple<0, N>, 0]>;
+
 type NegativeIndex<N extends number> = TSTypeUtilsInternals.MapIdx<
-  RelaxedExclude<IndexOfTuple<[0, ...MakeTuple<0, N>]>, 0>
+  RelaxedExclude<IndexInclusive<N>, 0>
 >;
 
 /** @internal */
diff --git a/packages/ts-type-utils/src/max.d.mts b/packages/ts-type-utils/src/max.d.mts
index 04cc13016c..7d5b66aa2d 100644
--- a/packages/ts-type-utils/src/max.d.mts
+++ b/packages/ts-type-utils/src/max.d.mts
@@ -10,32 +10,32 @@ declare namespace TSTypeUtilsInternals {
         : MaxImpl<N, [0, ...T]>;
 }
 
-// namespace _MaxImpl {
-//   /**
-//    * LEQ[3 | 5] == 0 | 1 | 2 | 3 | 4 | 5;
-//    */
+// declare namespace TSTypeUtilsInternals {
+//   /** `LEQ[3 | 5] == 0 | 1 | 2 | 3 | 4 | 5;` */
 //   type LEQ = {
 //     [N in Index<64>]: IndexOfTuple<[0, ...MakeTuple<0, N>]>;
 //   };
 
-//   /**
-//    * @returns Y if A == B otherwise N
-//    */
+//   /** @returns Y if A == B otherwise N */
 //   type Eq<A, B, Y, N> = [A] extends [B] ? ([B] extends [A] ? Y : N) : N;
 
+//   type ToLEQ<N extends number> = {
+//     [K in keyof LEQ]: [N] extends [RelaxedExclude<LEQ[K], K>] ? never : K;
+//   }[keyof LEQ];
+
 //   /**
 //    * The former part
 //    *
 //    * ```ts
 //    * type Main<
 //    *   N extends number,
-//    *   U extends number = ToLEQ<Extract<N, keyof LEQ>>
+//    *   U extends number = ToLEQ<Extract<N, keyof LEQ>>,
 //    * > = {
 //    *   [K in keyof LEQ]: Eq<U, LEQ[K], K, never>;
-//    * }
+//    * };
 //    * ```
 //    *
-//    * behaves like this
+//    * Behaves like this
 //    *
 //    * ```ts
 //    * type R = {
@@ -50,21 +50,16 @@ declare namespace TSTypeUtilsInternals {
 //    * }
 //    * ```
 //    */
-//   type Main<
-//     N extends number,
-//     U extends number = LEQ[Extract<N, keyof LEQ>]
-//   > = {
+//   type Main<N extends number, U extends number = ToLEQ<N>> = {
 //     [K in keyof LEQ]: Eq<U, LEQ[K], K, never>;
 //   }[keyof LEQ];
-// }
 
-// type Max<N extends Uint10> = _MaxImpl.Main<N>;
-
-// type _MaxImpl<N extends Index<64>, T extends readonly unknown[]> = {
-//   b: T['length'];
-//   r: _MaxImpl<N, [0, ...T]>;
-// }[[N] extends [Partial<T>['length']] ? 'b' : 'r'];
+//   // type MaxImpl<N extends Index<64>, T extends readonly unknown[]> = {
+//   //   b: T['length'];
+//   //   r: MaxImpl<N, [0, ...T]>;
+//   // }[[N] extends [Partial<T>['length']] ? 'b' : 'r'];
+// }
 
-// type Max<N extends Index<64>> = _MaxImpl<N, []>;
+// type Max<N extends Uint10> = TSTypeUtilsInternals.Main<N>;
 
 // https://stackoverflow.com/questions/62968955/how-to-implement-a-type-level-max-function-over-a-union-of-literals-in-typescri
diff --git a/packages/ts-type-utils/src/min.d.mts b/packages/ts-type-utils/src/min.d.mts
index bf5537aa9b..2f8eaed186 100644
--- a/packages/ts-type-utils/src/min.d.mts
+++ b/packages/ts-type-utils/src/min.d.mts
@@ -10,13 +10,11 @@ declare namespace TSTypeUtilsInternals {
         : MinImpl<N, [0, ...T]>;
 }
 
-// type _MinImpl<
-//   N extends Index<64>,
-//   Count extends number
-// > = IsNever<N> extends true
-//   ? never
-//   : 0 extends N
-//   ? Count
-//   : _MinImpl<Decrement<N>, Increment<Count> & number>;
-
 // type Min<N extends Index<64>> = _MinImpl<N, 0>;
+//
+// type MinImpl<N extends Index<64>, Count extends number> =
+//   IsNever<N> extends true
+//     ? never
+//     : 0 extends N
+//       ? Count
+//       : _MinImpl<Decrement<N>, Increment<Count> & number>;
diff --git a/packages/ts-type-utils/src/to-number.d.mts b/packages/ts-type-utils/src/to-number.d.mts
index 7ebac8cdbe..89ec74a163 100644
--- a/packages/ts-type-utils/src/to-number.d.mts
+++ b/packages/ts-type-utils/src/to-number.d.mts
@@ -2,30 +2,36 @@ type ToNumber<S extends `${number}`> = S extends `${infer N extends number}`
   ? N
   : never;
 
+/* TypeScript v4.8 以前では以下の実装が必要 */
+
 // type ToNumber<S extends `${number}`> =
-//   _ToNumberInternals._IsSmallNumber<S> extends true
-//     ? _MakeTupleInternals.MakeTupleImpl<unknown, S>['length']
+//   TSTypeUtilsInternals._IsSmallNumber<S> extends true
+//     ? TSTypeUtilsInternals.MakeTupleInternals.MakeTupleImpl<
+//         unknown,
+//         S,
+//         []
+//       >['length']
 //     : S;
 
-// namespace _ToNumberInternals {
+// declare namespace TSTypeUtilsInternals {
 //   // config
-//   type _DigitUpperLimit = 4;
+//   type DigitUpperLimit = 4;
 
-//   type _IsSmallNumber<S extends `${number}`> = _IsSmallNumberImpl<
+//   type IsSmallNumber<S extends `${number}`> = IsSmallNumberImpl<
 //     S,
-//     MakeTuple<unknown, _DigitUpperLimit>
+//     MakeTuple<unknown, DigitUpperLimit>
 //   >;
 
-//   type _Digit = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9;
+//   type Digit = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9;
 
-//   type _Tail<T extends string> = T extends `${_Digit}${infer U}` ? U : never;
+//   type Tail<T extends string> = T extends `${Digit}${infer U}` ? U : never;
 
-//   type _IsSmallNumberImpl<
+//   type IsSmallNumberImpl<
 //     S extends string,
-//     Counter extends readonly unknown[]
+//     Counter extends readonly unknown[],
 //   > = S extends ''
 //     ? true
 //     : TypeEq<Counter, readonly []> extends true
-//     ? false // reached the limit
-//     : _IsSmallNumberImpl<_Tail<S>, Tuple.Tail<Counter>>;
+//       ? false // reached the limit
+//       : IsSmallNumberImpl<Tail<S>, Tuple.Tail<Counter>>;
 // }
diff --git a/packages/ts-type-utils/src/uint-range.d.mts b/packages/ts-type-utils/src/uint-range.d.mts
index 71ecb955c1..98090e640d 100644
--- a/packages/ts-type-utils/src/uint-range.d.mts
+++ b/packages/ts-type-utils/src/uint-range.d.mts
@@ -3,8 +3,6 @@ type UintRange<Start extends number, End extends number> = RelaxedExclude<
   Index<Start>
 >;
 
-type IndexInclusive<N extends number> = IndexOfTuple<[...MakeTuple<0, N>, 0]>;
-
 type UintRangeInclusive<
   MinValue extends number,
   MaxValue extends number,
diff --git a/packages/ts-type-utils/src/utils.d.mts b/packages/ts-type-utils/src/utils.d.mts
index 6047cbb995..1431d023db 100644
--- a/packages/ts-type-utils/src/utils.d.mts
+++ b/packages/ts-type-utils/src/utils.d.mts
@@ -10,14 +10,17 @@ type TypeEq<A, B> =
 
 type TypeExtends<A, B> = A extends B ? true : false;
 
+/** Extract from T those types that are assignable to U */
+type RelaxedExtract<T, U> = T extends U ? T : never;
+
+/** From T, pick a set of properties whose keys are in the union K */
+type RelaxedPick<T, K> = Pick<T, RelaxedExtract<keyof T, K>>;
+
 /** Exclude from T those types that are assignable to U */
 type RelaxedExclude<T, U> = T extends U ? never : T;
 
 /** Construct a type with the properties of T except for those in type K. */
-type RelaxedOmit<T, K extends keyof never> = Pick<
-  T,
-  RelaxedExclude<keyof T, K>
->;
+type RelaxedOmit<T, K> = Pick<T, RelaxedExclude<keyof T, K>>;
 
 /* type constants */
 
@@ -154,41 +157,15 @@ type MutableArrayOfLength<N extends number, Elm> = Mutable<
 
 // https://qiita.com/uhyo/items/80ce7c00f413c1d1be56
 
-type MutableArrayOfLengthOrMore<N extends number, Elm> = MutableArrayAtLeastLen<
-  N,
-  Elm
->;
 type MutableArrayAtLeastLen<N extends number, Elm> = Mutable<
   ArrayAtLeastLen<N, Elm>
 >;
 
-type ArrayOfLengthOrMore<N extends number, Elm> = ArrayAtLeastLen<N, Elm>;
 type ArrayAtLeastLen<N extends number, Elm> = readonly [
   ...MakeTuple<Elm, N>,
   ...Elm[],
 ];
 
-// type ArrayAtLeastLen<N extends number, Elm> = ArrayAtLeastLenRec<
-//   N,
-//   Elm,
-//   Elm[],
-//   []
-// >;
-
-// type ArrayAtLeastLenRec<
-//   Num,
-//   Elm,
-//   T extends readonly unknown[],
-//   C extends readonly unknown[],
-// > = C extends { length: Num }
-//   ? T
-//   : ArrayAtLeastLenRec<
-//       Num,
-//       Elm,
-//       readonly [Elm, ...T],
-//       readonly [unknown, ...C]
-//     >;
-
 type MergeIntersection<R extends UnknownRecord> = {
   [K in keyof R]: R[K];
 };
diff --git a/packages/ts-type-utils/test/array-of-length.mts b/packages/ts-type-utils/test/array-of-length.mts
index 2599c75cb2..00ef086b39 100644
--- a/packages/ts-type-utils/test/array-of-length.mts
+++ b/packages/ts-type-utils/test/array-of-length.mts
@@ -14,6 +14,6 @@ expectType<ArrayOfLength<3, 0>, readonly [0, 0, 0]>('=');
 expectType<ArrayOfLength<4, 1>, readonly [1, 1, 1, 1]>('=');
 expectType<MutableArrayOfLength<4, 1>, [1, 1, 1, 1]>('=');
 
-expectType<ArrayOfLengthOrMore<0, 0>, readonly 0[]>('=');
-expectType<ArrayOfLengthOrMore<3, 0>, readonly [0, 0, 0, ...0[]]>('=');
-expectType<ArrayOfLengthOrMore<4, 1>, readonly [1, 1, 1, 1, ...1[]]>('=');
+expectType<ArrayAtLeastLen<0, 0>, readonly 0[]>('=');
+expectType<ArrayAtLeastLen<3, 0>, readonly [0, 0, 0, ...0[]]>('=');
+expectType<ArrayAtLeastLen<4, 1>, readonly [1, 1, 1, 1, ...1[]]>('=');