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40 lines
1.1 KiB
JavaScript
40 lines
1.1 KiB
JavaScript
// @flow
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import RuntimeError from './runtime_error.js';
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import type {Expression} from './expression.js';
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export type Stops = Array<[number, Expression]>;
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/**
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* Returns the index of the last stop <= input, or 0 if it doesn't exist.
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* @private
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*/
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export function findStopLessThanOrEqualTo(stops: Array<number>, input: number): number {
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const lastIndex = stops.length - 1;
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let lowerIndex = 0;
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let upperIndex = lastIndex;
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let currentIndex = 0;
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let currentValue, nextValue;
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while (lowerIndex <= upperIndex) {
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currentIndex = Math.floor((lowerIndex + upperIndex) / 2);
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currentValue = stops[currentIndex];
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nextValue = stops[currentIndex + 1];
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if (currentValue <= input) {
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if (currentIndex === lastIndex || input < nextValue) { // Search complete
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return currentIndex;
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}
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lowerIndex = currentIndex + 1;
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} else if (currentValue > input) {
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upperIndex = currentIndex - 1;
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} else {
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throw new RuntimeError('Input is not a number.');
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}
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}
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return 0;
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}
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