#TypeScript experiment: dropping elements from a tuple
type Drop<Tuple extends Array<unknown>, Num extends number, Counter extends Array<boolean> = []> =
Counter['length'] extends Num
? Tuple
: Tuple extends [unknown, ...infer Rest extends Array<unknown>]
? Drop<Rest, Num, [true, ...Counter]>
: Tuple
;
type X = Drop<['a', 'b', 'c'], 2>; // ["c"]
`Counter` feels hacky but not sure it can be avoided.
Axel Rauschmayer
npub10f…ardvy
2025-01-25 17:16:55 UTC
Author Public Key
npub10faqj7xvgmhhl42glvf9u5wqfhnafjnrjst6yx6k4227xugupvuqzardvyPublished at
2025-01-25 17:16:55 UTCEvent JSON
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"content": "#TypeScript experiment: dropping elements from a tuple\n\ntype Drop\u003cTuple extends Array\u003cunknown\u003e, Num extends number, Counter extends Array\u003cboolean\u003e = []\u003e =\n Counter['length'] extends Num\n ? Tuple\n : Tuple extends [unknown, ...infer Rest extends Array\u003cunknown\u003e]\n ? Drop\u003cRest, Num, [true, ...Counter]\u003e\n : Tuple\n;\ntype X = Drop\u003c['a', 'b', 'c'], 2\u003e; // [\"c\"]\n\n`Counter` feels hacky but not sure it can be avoided.",
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