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Chris Tate
b3d3101550
- Lower unshift and reverse through the C and LLVM backends. - Preserve spread, mutation, evaluation-order, and reference-counting semantics. - Add runtime, differential, and surface-manifest coverage.
56 lines
2.0 KiB
TypeScript
56 lines
2.0 KiB
TypeScript
// Static Array.prototype.unshift and mutating reverse: variadic insertion
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// preserves source order, returns the new length, and evaluates every
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// argument before the first mutation. reverse mutates in place and returns
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// the receiver identity.
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const nums: number[] = [3, 4];
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console.log(nums.unshift(1, 2), nums.join(","));
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console.log(nums.unshift(), nums.join(","));
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const observed: number[] = [10];
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console.log(observed.unshift(observed.length, observed.length));
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console.log(observed.join(","));
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// A single same-element array or Set spread keeps iteration order. The
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// self-spread form snapshots the original values before front insertion.
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const fromArray: number[] = [7, 8];
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console.log(nums.unshift(...fromArray), nums.join(","));
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const fromSet = new Set<number>([5, 6]);
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console.log(nums.unshift(...fromSet), nums.join(","));
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const self: number[] = [1, 2, 3];
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console.log(self.unshift(...self), self.join(","));
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// reverse returns THE receiver: mutating the result mutates the original.
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const reversed = nums.reverse();
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console.log(nums.join(","));
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reversed.push(99);
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console.log(nums.join(","));
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console.log(reversed.reverse().unshift(0), nums.join(","));
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// Scalar and refcounted element representations all use the same slot
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// mutation without copying or releasing the elements.
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const bits: boolean[] = [false, true];
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bits.unshift(true, false);
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console.log(bits.reverse().join(","));
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interface Row {
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id: number;
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label: string;
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}
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const rows: Row[] = [{ id: 2, label: "b" }];
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const first: Row = { id: 1, label: "a" };
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rows.unshift(first);
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const sameRows = rows.reverse();
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sameRows[1]!.label = "A";
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console.log(rows[0]!.id, rows[1]!.label, rows.length);
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const optional: (string | undefined)[] = ["tail"];
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optional.unshift(undefined, "head");
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optional.reverse();
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console.log(optional.length, optional[0] ?? "-", optional[1] ?? "-", optional[2] === undefined);
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console.log([1, 2, 3].reverse().join("-"));
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const empty: string[] = [];
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const emptyResult = empty.reverse();
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emptyResult.unshift("x");
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console.log(empty.join(","));
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