Support for Enumerate and Range

[Anatole Lucet]

I think an Enumerate and Range generic could be a nice addition to the Number/Tuple namespace.
I've been using these generics to generate lists of unioned numbers (maybe this could be a tuple instead of a union 🤷) for discriminated unions of objects (e.g. http responses discriminated by status code).

See:
https://www.typescriptlang.org/play?#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

PS amazing work on this lib. I love the overall design and the DX truly looks fantastic!

[Gabriel Vergnaud]

Great suggestion

[Brandon McConnell]

@gvergnaud @AnatoleLucet I just realized that one of the issues I opened duplicates this one: #37

I'll close that one and continue the discussion here:

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Definition

type Enumerate<N extends number, Acc extends number[] = []> = Acc['length'] extends N
  ? Acc[number]
  : Enumerate<N, [...Acc, Acc['length']]>;

type IntRange<F extends number, T extends number> = Exclude<Enumerate<T>, Enumerate<F>> | T;

Usage

type CustomRange = IntRange<20, 300>; // -> 20 | 21 | ... many more ... | 300

Disclaimer & credit

This type is inspired (99% copied) from this StackOverflow answer by AlexG, with a slight modification to include the last number in the series (| T). Without this change, IntRange<20, 300> would match 20–299 instead or 20–300.

[Brandon McConnell]

Per that last disclaimer, I think it could be more intuitive to include the last/max number. So instead of IntRange<100, 200>, we could use IntRange<100, 199>.

We could even make the option of whether to include the end or not a second boolean arg, which I personally think should default to true. With that enabled, if you wanted to keep the min and max values the same and not use the "…99" values, you could do this—

type Informational = IntRange<100, 200, false>;

This would work identically to the previous example. Here is the modified type to support that:

type Enumerate<N extends number, Acc extends number[] = []> = Acc['length'] extends N
  ? Acc[number]
  : Enumerate<N, [...Acc, Acc['length']]>;
type IntRange<F extends number, T extends number, IncludeEnd = true> = IncludeEnd extends true ? (Exclude<Enumerate<T>, Enumerate<F>> | T) : (Exclude<Enumerate<T>, Enumerate<F>>);

type WithEnd    = IntRange<20, 300>;        // -> 20 | 21 | ... many more ... | 300
type WithoutEnd = IntRange<20, 300, false>; // -> 20 | 21 | ... many more ... | 299

[Gabriel Vergnaud]

Hey! This is related to the PR I opened adding a Tuples.Range function: #40

I think we should implement Unions.Range in terms of Tuples.Range

[Gabriel Vergnaud]

Well, here is a PR doing this: #41

[Gabriel Vergnaud]

(closing because this has been implemented)