23 lines
552 B
TypeScript
23 lines
552 B
TypeScript
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function map<T, U>(items: T[], f: (x: T) => U): U[]{
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return items.map(f);
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}
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function identity<T>(x: T) {
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return x;
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}
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function singleton<T>(x: T) {
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return [x];
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}
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var xs = [1, 2, 3];
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// Have compiler check that we get the correct types
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var v1: number[];
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var v1 = xs.map(identity); // Error if not number[]
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var v1 = map(xs, identity); // Error if not number[]
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var v2: number[][];
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var v2 = xs.map(singleton); // Error if not number[][]
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var v2 = map(xs, singleton); // Error if not number[][]
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