src/vs/editor/common/diff/algorithms/myersDiffAlgorithm.ts/FastArrayNegativeIndices/get
class FastArrayNegativeIndices:	get(idx: number): T {
		if (idx < 0) {
			idx = -idx - 1;
			return this.negativeArr[idx];
		} else {
			return this.positiveArr[idx];
		}
	}