periodic-function/test.js at master · scijs/periodic-function · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
import test from 'node:test'
import assert from 'node:assert/strict'
import { sine, cosine, sawtooth, square, triangle, trapezoid, pulse, clausen, noise, interpolate, step, fourier, wavetable } from './index.js'

const ε = 1e-6
const near = (a, b) => Math.abs(a - b) < ε

test('sine', () => {
	assert.ok(near(sine(0), 0))
	assert.ok(near(sine(0.25), 1))
	assert.ok(near(sine(0.5), 0))
	assert.ok(near(sine(0.75), -1))
	assert.ok(near(sine(-0.75), sine(0.25)))
	// phase shift
	assert.ok(near(sine(0, 0.25), 1))   // sine with 0.25 phase = cosine
})

test('cosine', () => {
	assert.ok(near(cosine(0), 1))
	assert.ok(near(cosine(0.25), 0))
	assert.ok(near(cosine(0.5), -1))
	assert.ok(near(cosine(0.75), 0))
	// cosine = sine shifted by 0.25
	assert.ok(near(cosine(0.3), sine(0.3, 0.25)))
})

test('sawtooth', () => {
	assert.ok(near(sawtooth(0), 1))
	assert.ok(near(sawtooth(0.5), 0))
	assert.ok(near(sawtooth(0.875), -0.75))
	assert.ok(near(sawtooth(-0.75), sawtooth(0.25)))
})

test('square', () => {
	assert.equal(square(0), 1)
	assert.equal(square(0.25), 1)
	assert.equal(square(0.5), -1)
	assert.equal(square(0.75), -1)
	// duty cycle
	assert.equal(square(0.05, 0.1), 1)
	assert.equal(square(0.15, 0.1), -1)
	assert.equal(square(-0.75), square(0.25))
})

test('triangle', () => {
	assert.equal(triangle(0), 1)
	assert.equal(triangle(0.25), 0)
	assert.equal(triangle(0.5), -1)
	assert.equal(triangle(0.75), 0)
	assert.ok(near(triangle(-0.75), triangle(0.25)))
	// ratio=0: ascending ramp
	assert.equal(triangle(0, 0), -1)
	assert.equal(triangle(0.5, 0), 0)
	// ratio=1: descending (same as sawtooth)
	assert.ok(near(triangle(0.3, 1), sawtooth(0.3)))
})

test('trapezoid', () => {
	// default: rise [0,0.25], high [0.25,0.5], fall [0.5,0.75], low [0.75,1]
	assert.equal(trapezoid(0), -1)
	assert.equal(trapezoid(0.125), 0)    // midpoint of rise
	assert.equal(trapezoid(0.25), 1)     // top of rise
	assert.equal(trapezoid(0.4), 1)      // sustain high
	assert.equal(trapezoid(0.625), 0)    // midpoint of fall
	assert.equal(trapezoid(0.75), -1)    // bottom of fall
	assert.equal(trapezoid(0.9), -1)     // sustain low
	// square-like: trapezoid(t, 0, 0.5, 0.5)
	assert.equal(trapezoid(0, 0, 0.5, 0.5), 1)
	assert.equal(trapezoid(0.49, 0, 0.5, 0.5), 1)
	assert.equal(trapezoid(0.5, 0, 0.5, 0.5), -1)
})

test('pulse', () => {
	assert.equal(pulse(0), 1)
	assert.equal(pulse(0.01), 0)
	assert.equal(pulse(0.5), 0)
	// with width
	assert.equal(pulse(0.05, 0.1), 1)
	assert.equal(pulse(0.15, 0.1), 0)
	assert.ok(near(pulse(-0.75), pulse(0.25)))
})

test('clausen', () => {
	assert.ok(near(clausen(0), 0))
	assert.ok(near(clausen(0.5), 0))       // antisymmetric around 0.5
	assert.ok(near(clausen(-0.75), clausen(0.25)))
})

test('noise', () => {
	// periodic: same t gives same value
	assert.equal(noise(0), noise(0))
	assert.equal(noise(0.5), noise(0.5))
	assert.equal(noise(1.5), noise(0.5))
	// values in [-1, 1]
	for (let i = 0; i < 10; i++) {
		let v = noise(i / 10)
		assert.ok(v >= -1 && v <= 1)
	}
})

test('interpolate', () => {
	const samples = [0, 0.5, 1, 0.5, 0]
	assert.equal(interpolate(0, samples), 0)
	assert.ok(near(interpolate(0.2, samples), 0.5))
	assert.ok(near(interpolate(0.4, samples), 1))
	assert.ok(near(interpolate(0.1, samples), 0.25))
})

test('step', () => {
	const samples = [0, 1, 2, 3]
	assert.equal(step(0, samples), 0)
	assert.equal(step(0.25, samples), 1)
	assert.equal(step(0.5, samples), 2)
	assert.equal(step(0.75, samples), 3)
	assert.equal(step(1, samples), 0)   // wraps
})

test('fourier', () => {
	// pure sine: imag[1]=1 → sin(2πt)
	assert.ok(near(fourier(0, null, [0, 1]), 0))
	assert.ok(near(fourier(0.25, null, [0, 1]), 1))
	assert.ok(near(fourier(0.75, null, [0, 1]), -1))
	// pure cosine: real[1]=1 → cos(2πt)
	assert.ok(near(fourier(0, [0, 1], null), 1))
	assert.ok(near(fourier(0.25, [0, 1], null), 0))
	// DC offset: real[0]=0.5
	assert.ok(near(fourier(0.3, [0.5], null), 0.5))
})

test('wavetable', () => {
	// pure sine wavetable (normalized)
	const tbl = wavetable(null, [0, 1], {size: 1024})
	assert.ok(near(tbl[0], 0))
	assert.ok(near(tbl[256], 1))        // quarter period = peak
	assert.ok(near(tbl[512], 0))
	assert.ok(near(tbl[768], -1))
	assert.ok(tbl instanceof Float32Array)
	assert.equal(tbl.length, 1024)

	// normalization
	const tbl2 = wavetable(null, [0, 1, 0, 0.5], {size: 256})
	let max = 0
	for (let v of tbl2) if (Math.abs(v) > max) max = Math.abs(v)
	assert.ok(near(max, 1))

	// no normalization
	const tbl3 = wavetable(null, [0, 1], {size: 4, normalize: false})
	assert.ok(near(tbl3[1], 1))         // sin(π/2) = 1
})