D6048.diff
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	diff --git a/lib/utils/math-utils.js b/lib/utils/math-utils.js
	new file mode 100644
	--- /dev/null
	+++ b/lib/utils/math-utils.js
	@@ -0,0 +1,13 @@
	+// @flow
	+
	+function leastPositiveResidue(dividend: number, modulus: number): number {
	+ // the smallest positive of x is integer k such that
	+ // x is congruent to k (mod n)
	+ // in our case we only consider n > 0
	+ if (modulus <= 0) {
	+ throw new Error(`modulus must be greater than 0, but was ${modulus}`);
	+ }
	+ return dividend - Math.floor(dividend / modulus) * modulus;
	+}
	+
	+export { leastPositiveResidue };
	diff --git a/lib/utils/math-utils.test.js b/lib/utils/math-utils.test.js
	new file mode 100644
	--- /dev/null
	+++ b/lib/utils/math-utils.test.js
	@@ -0,0 +1,23 @@
	+// @flow
	+
	+import { leastPositiveResidue } from './math-utils';
	+
	+describe('leastPositiveResidue', () => {
	+ it('x should be equal to 2 for x ≡ 8 (mod 3)', () => {
	+ expect(leastPositiveResidue(8, 3)).toEqual(2);
	+ });
	+
	+ it('x should be equal to 5 for x ≡ 19 (mod 7)', () => {
	+ expect(leastPositiveResidue(19, 7)).toEqual(5);
	+ });
	+
	+ it('x should be equal to 7 for x ≡ -3 (mod 11)', () => {
	+ expect(leastPositiveResidue(-3, 10)).toEqual(7);
	+ });
	+
	+ it('function should throw error', () => {
	+ expect(() => leastPositiveResidue(5, -1)).toThrow(
	+ 'modulus must be greater than 0, but was -1',
	+ );
	+ });
	+});