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@Grubba27
Created April 20, 2022 01:13
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FizzBuzz made in typelevel
type Reverse<A> =
`${A}` extends `${infer AH}${infer AT}`
? `${Reverse<AT>}${AH}` : A
type Digs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
type DigsNext<I = Digs, R = {}> =
I extends [infer Head, infer Next, ...infer Tail]
? DigsNext<[Next, ...Tail], R & Record<Head, Next>>
: { [K in keyof R]: R[K] }
type DigsPrev = { [K in keyof DigsNext as DigsNext[K]]: K }
type AddOne<A> =
A extends `${infer AH}${infer AT}`
? AH extends '9' ? `0${AddOne<AT>}` : `${DigsNext[AH]}${AT}`
: `1`
type SubOne<A> =
A extends `${infer AH}${infer AT}`
? AH extends '0' ? `9${SubOne<AT>}` : `${DigsPrev[AH]}${AT}`
: never
type Add<A, B> =
A extends `${infer AH}${infer AT}` ?
B extends `${infer BH}${infer BT}`
? BH extends '0' ? `${AH}${Add<AT, BT>}` : Add<AddOne<A>, SubOne<B>>
: A : B
type Mul<A, B, R = '0'> =
A extends '0' ? R :
B extends '0' ? R :
A extends `${infer AH}${infer AT}`
? AH extends '0' ? Mul<AT, `0${B}`, R> : Mul<SubOne<A>, B, Add<R, B>>
: R
type Multiply<A extends string | number | bigint, B extends string | number | bigint> =
Reverse<Mul<Reverse<A>, Reverse<B>>>
type Division<
W extends number,
D extends number,
Error extends any = never,
Q extends string = '0'
> =
W extends 0
? Q extends never ? Error : Q
: W extends never ? Error : Division<Subtract<W, D>, D, Error, AddOne<Q>>
type ConstructTuple<
L extends number,
R extends unknown[] = []
> = R["length"] extends L
? R
: ConstructTuple<L, [...R, unknown]>
type Subtract<
M extends number,
S extends number
> = ConstructTuple<M> extends [...subtrahend: ConstructTuple<S>, ...rest: infer Rest]
? Rest["length"]
: never
const div: Division<9, 3> = "3"
const div: Division<15, 3> = "5"
type FizzBuzzValidator<
V extends number
> =
Division<V, 3> extends never
? never
: Division<V, 5> extends never
? never
: 'FizzBuzz'
type BuzzValidator<
V extends number
> =
Division<V, 3> extends never
? never
: 'Buzz'
type FizzValidator<
V extends number
> =
Division<V, 5> extends never
? never
: 'Fizz'
type FizzBuzz
<V extends number> =
FizzBuzzValidator<V> extends never
? FizzValidator<V> extends never
? BuzzValidator<V> extends never
? V
:'Buzz'
:'Fizz'
:'FizzBuzz'
const res: FizzBuzz<2> // 2
const buzz: FizzBuzz<3> // Buzz
const fizz: FizzBuzz<5> // Fizz
const fizzBuzz: FizzBuzz<15> // FizzBuzz
type FizzBuzzArr<
V extends Array<number>,
A extends Array<any> = []
> =
V extends [infer E, ...infer D]
? FizzBuzzArr<D, [...A, ...[FizzBuzz<E>]]>
: A
const FIZZBUZZZZ: FizzBuzzArr<[1,2,3,4,5,6,7,8,9, 15]> // [1, 2, "Buzz", 4, "Fizz", "Buzz", 7, 8, "Buzz", "FizzBuzz"]
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