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palladin/powerset.ts

Created June 2, 2022 14:06
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Type level PowerSet in TypeScript
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powerset.ts
type Append<T, TArray> = TArray extends [infer TCurrent, ...infer Rest] ?
TCurrent extends any[] ? [[T, ...TCurrent], ...Append<T, Rest>] : never
: []
type PowerSet<TArray extends any[]> =
TArray extends [infer TCurrent, ...infer Rest] ? [...Append<TCurrent, PowerSet<Rest>>, ...PowerSet<Rest>] : [[]]
type Test = PowerSet<[1, 2, 3]> // [[1, 2, 3], [1, 2], [1, 3], [1], [2, 3], [2], [3], []]
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