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aa5c9eef76
Incorporating unit offsets into the internal "value" of the unit causes more problems than it solves. This commit ends that practice and instead only uses the offset when converting units or when computing the absolute value of a unit. Further, it makes it an error to compute the sign of a unit with an offset, since that is inherently ambiguous: there is no way to tell whether "-5 degC" is a temperature change, in which case it is definitely negative, or if it is a specific temperature of something, in which case it is "positive" in the sense of being above absolute zero. (Unclear how valuable this latter concept is anyway, given that there are no negative temperatures possible in that sense...) Adds several tests for the various problems the former practice caused, including all four basic arithmetic operations on units with offsets. Co-authored-by: Jos de Jong <wjosdejong@gmail.com>
110 lines
4.4 KiB
JavaScript
110 lines
4.4 KiB
JavaScript
// test sign
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import assert from 'assert'
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import approx from '../../../../tools/approx.js'
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import math from '../../../../src/defaultInstance.js'
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const bignumber = math.bignumber
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const fraction = math.fraction
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const complex = math.complex
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describe('sign', function () {
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it('should calculate the sign of a boolean', function () {
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assert.strictEqual(math.sign(true), 1)
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assert.strictEqual(math.sign(false), 0)
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})
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it('should calculate the sign of a number', function () {
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assert.strictEqual(math.sign(3), 1)
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assert.strictEqual(math.sign(-3), -1)
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assert.strictEqual(math.sign(0), 0)
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})
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it('should calculate the sign of a big number', function () {
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assert.deepStrictEqual(math.sign(bignumber(3)), bignumber(1))
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assert.deepStrictEqual(math.sign(bignumber(-3)), bignumber(-1))
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assert.deepStrictEqual(math.sign(bignumber(0)), bignumber(0))
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})
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it('should calculate the sign of a fraction', function () {
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const a = fraction(0.5)
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assert(math.sign(a) instanceof math.Fraction)
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assert.strictEqual(math.sign(a).toString(), '1')
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assert.strictEqual(math.sign(fraction(-0.5)).toString(), '-1')
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assert.strictEqual(a.toString(), '0.5')
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})
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it('should calculate the sign of a complex value', function () {
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approx.deepEqual(math.sign(math.complex(2, -3)), math.complex(0.554700196225229, -0.832050294337844))
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})
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it('should calculate the sign of a unit', function () {
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assert.strictEqual(math.sign(math.unit('5 cm')), 1)
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assert.strictEqual(math.sign(math.unit('-5 kg')), -1)
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assert.strictEqual(math.sign(math.unit('0 mol/s')), 0)
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/* sign is ambiguous on units with offset, because you don't know if
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* -3 degC is the difference between two temperatures, in which case
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* it is definitely negative, or an actual temperature of something,
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* in which case it is arguably positive. So actually mathjs should
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* throw an error, which we will test below. Formerly:
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assert.strictEqual(math.sign(math.unit('-283.15 degC')), -1)
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assert.strictEqual(math.sign(math.unit('-273.15 degC')), 0)
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assert.strictEqual(math.sign(math.unit('-263.15 degC')), 1)
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*/
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assert.deepStrictEqual(math.sign(math.unit(bignumber(5), 'cm')), bignumber(1))
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assert.deepStrictEqual(math.sign(math.unit(bignumber(-5), 'cm')), bignumber(-1))
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assert.deepStrictEqual(math.sign(math.unit(fraction(5), 'cm')), fraction(1))
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assert.deepStrictEqual(math.sign(math.unit(fraction(-5), 'cm')), fraction(-1))
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assert.deepStrictEqual(math.sign(math.unit(complex(3, 4), 'mi')), complex(0.6, 0.8))
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})
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it('should throw an error on a valueless unit or a unit with offset', () => {
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assert.throws(() => math.sign(math.unit('ohm')), TypeError)
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assert.throws(() => math.sign(math.unit('-3 degC')), /ambiguous/)
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})
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it('should throw an error when used with a string', function () {
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assert.throws(function () { math.sign('hello world') })
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})
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it('should return a matrix of the signs of each elements in the given array', function () {
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assert.deepStrictEqual(math.sign([-2, -1, 0, 1, 2]), [-1, -1, 0, 1, 1])
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})
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it('should return a matrix of the signs of each elements in the given matrix', function () {
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assert.deepStrictEqual(math.sign(math.matrix([-2, -1, 0, 1, 2])), math.matrix([-1, -1, 0, 1, 1]))
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})
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it('should throw an error in case of invalid number of arguments', function () {
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assert.throws(function () { math.sign() }, /TypeError: Too few arguments/)
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assert.throws(function () { math.sign(1, 2) }, /TypeError: Too many arguments/)
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})
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it('should throw an in case of wrong type of arguments', function () {
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assert.throws(function () { math.sign(null) }, /TypeError: Unexpected type of argument/)
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})
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describe('sign(0) should return 0', function () {
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it('number', function () {
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assert.strictEqual(math.sign(0), 0)
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})
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it('bignumber', function () {
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assert.deepStrictEqual(math.sign(math.bignumber(0)), math.bignumber(0))
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})
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it('complex', function () {
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assert.deepStrictEqual(math.sign(math.complex(0)), math.complex(0))
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})
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})
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it('should throw an in case of wrong type of arguments', function () {
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assert.throws(function () { math.sign(null) }, /TypeError: Unexpected type of argument/)
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})
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it('should LaTeX sign', function () {
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const expression = math.parse('sign(-4)')
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assert.strictEqual(expression.toTex(), '\\mathrm{sign}\\left(-4\\right)')
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})
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})
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