TypeScript

var Id = <T>(x: T) => ({ cata: (alg: (a: T) => void) => alg(x), map: <U>(f: (y: T) => U) => Id<U>(f(x)) }) var t = Id<number>(2).map(x => x + 3); t.cata(console.log) //# sourceMappingURL=app.js.map

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Use pre-released features

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