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2dbf32548f
Prior to this change, combinations(42,21) did not return an integer, despite its value being well below MAX_SAFE_INTEGER. Now the multiplications and divisions are balanced to try to keep the intermediate results within the safe range. Adds a couple of tests for larger values of combinations(). Resolves #2413. Co-authored-by: Jos de Jong <wjosdejong@gmail.com>
46 lines
2.4 KiB
JavaScript
46 lines
2.4 KiB
JavaScript
import assert from 'assert'
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import math from '../../../../src/defaultInstance.js'
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const combinations = math.combinations
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describe('combinations', function () {
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it('should calculate the combinations of a number taking k at a time', function () {
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assert.strictEqual(combinations(0, 0), 1)
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assert.strictEqual(combinations(7, 5), 21)
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assert.strictEqual(combinations(20, 15), 15504)
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assert.strictEqual(combinations(63, 7), 553270671)
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assert.strictEqual(combinations(25, 6), 177100)
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assert.strictEqual(combinations(42, 21), 538257874440)
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assert.strictEqual(combinations(44, 21), 2012616400080)
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})
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it('should calculate the combinations of n items taken k at a time with BigNumbers', function () {
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assert.deepStrictEqual(combinations(math.bignumber(7), math.bignumber(5)), math.bignumber(21))
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assert.deepStrictEqual(combinations(math.bignumber(20), math.bignumber(15)), math.bignumber(15504))
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assert.deepStrictEqual(combinations(math.bignumber(63), math.bignumber(7)), math.bignumber(553270671))
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assert.deepStrictEqual(combinations(math.bignumber(25), math.bignumber(6)), math.bignumber(177100))
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assert.deepStrictEqual(combinations(math.bignumber(42), math.bignumber(21)), math.bignumber(538257874440))
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assert.deepStrictEqual(combinations(math.bignumber(44), math.bignumber(21)), math.bignumber(2012616400080))
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})
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it('should not work with non-integer and negative input', function () {
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assert.throws(function () { combinations(-12, 6) }, TypeError)
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assert.throws(function () { combinations(12, -6) }, TypeError)
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assert.throws(function () { combinations(0.5, 3) }, TypeError)
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assert.throws(function () { combinations(4, 0.5) }, TypeError)
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assert.throws(function () { combinations(3, 5) }, TypeError)
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assert.throws(function () { combinations(math.bignumber(3), math.bignumber(5)) }, TypeError)
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assert.throws(function () { combinations(math.bignumber(3.5), math.bignumber(-3)) }, TypeError)
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assert.throws(function () { combinations(math.bignumber(3.5), 1 / 3) }, TypeError)
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})
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it('should not work with the wrong number or type of arguments', function () {
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assert.throws(function () { combinations(5, 3, 2) })
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assert.throws(function () { combinations(true, 'hello world') })
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})
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it('should LaTeX combinations', function () {
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const expression = math.parse('combinations(3,2)')
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assert.strictEqual(expression.toTex(), '\\binom{3}{2}')
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})
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})
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