periodic-function/test.js

Collection of periodic functions

'use strict'

const t = require('tape')
const fn = require('./')
const almost = require('almost-equal')

function draw(fn, ...args) {
	if (typeof document === 'undefined') return

	let arr = populate(fn, 32, ...args)

	let canvas = document.body.appendChild(document.createElement('canvas'))
	let ctx = canvas.getContext('2d')
	canvas.width = arr.length
	canvas.height = 32
	let w = canvas.width * .75, h = canvas.height*.75

	ctx.beginPath()
	// ctx.moveTo(canvas.width*.125,canvas.height*.625)
	for (let i = 0, l = arr.length; i < l; i++) {
		// ctx.fillRect(w*i/l, h*.5, 1, -(arr[i]*.5)*h )
		ctx.lineTo(w*i/l + canvas.width*.125, canvas.height*.5-(arr[i]*.5)*h )
	}
	// ctx.lineTo(canvas.width*.875,canvas.height*.625)
	ctx.lineWidth = 2;
	ctx.stroke()
	ctx.closePath()
}

function populate(fn, N, ...args) {
	return Array.from({length: N}, (v, i) => fn(i/N, ...args))
}


t('sin', t => {
	draw(fn.sine)
	var sin = populate(fn.sine, 1024);
	t.equal(sin[0], 0);
	t.equal(sin[~~(1024/4)], 1);
	t.ok(almost(sin[~~(1024/2)], 0, 0.0001, 0.0001));
	t.equal(fn.sine(-.75), fn.sine(.25))
	t.end()
});

t('cos', t => {
	draw(fn.sine, .25)
	var cos = populate(fn.sine, 4, .25);
	t.equal(cos[0], 1);
	t.ok(almost(cos[1], 0, 0.0001, 0.0001));
	t.equal(cos[2], -1);
	t.ok(almost(cos[3], 0, 0.0001, 0.0001));
	t.end()
});

t('delta', t => {
	draw(fn.pulse)
	var delta = populate(fn.pulse, 4);
	t.equal(delta[0], 1);
	t.equal(delta[1], 0);
	t.equal(delta[2], 0);
	t.equal(delta[3], 0);
	t.end()
});

t('pulse', t => {
	var pulse = populate(fn.pulse, 10, 0);
	t.equal(pulse[0], 1);
	t.equal(pulse[1], 0);
	t.equal(pulse[9], 0);
	t.equal(fn.pulse(-.75), fn.pulse(.25))
	t.end()
});

t('square', t => {
	draw(fn.square)
	var square = populate(fn.square, 10);
	t.equal(square[0], 1);
	t.equal(square[4], 1);
	t.equal(square[5], -1);
	t.equal(square[9], -1);

	draw(fn.square, .1)
	var square = populate(fn.square, 10, .1);
	t.equal(square[0], 1);
	t.equal(square[4], -1);
	t.equal(square[5], -1);
	t.equal(square[9], -1);
	t.equal(fn.square(-.75), fn.square(.25))
	t.end()
});


t('triangle', t => {
	draw(fn.triangle)
	var triangle = populate(fn.triangle, 8);
	t.equal(triangle[0], 1);
	t.equal(triangle[1], 0.5);
	t.equal(triangle[2], 0);
	t.equal(triangle[3], -.5);
	t.equal(triangle[4], -1);
	t.equal(triangle[6], 0);
	t.equal(triangle[7], 0.5);
	t.equal(fn.triangle(-.75), fn.triangle(.25))
	t.end()
});

t('triangle ratio', t => {
	draw(fn.triangle, .25)
	var triangle = populate(fn.triangle, 8, .25);
	t.equal(triangle[2], -1)
	t.end()
});

t('saw', t => {
	draw(fn.sawtooth)
	var saw = populate(fn.sawtooth, 8);
	t.equal(saw[0], 1);
	t.equal(saw[7], -.75);

	draw(fn.sawtooth, true)
	var sawi = populate(fn.sawtooth, 8, true);
	t.equal(sawi[0], -1);
	t.equal(sawi[7], .75);

	t.equal(fn.sawtooth(-.75), fn.sawtooth(.25))
	t.end()
});


t('fourier', t => {
	draw(fn.fourier, [0, 1, 0, .5], [0, .5, 0, .1], true)
	var series = populate(fn.fourier, 8, [1, .5, .25, .125], true);
	t.equal(series[0], 1)

	populate(fn.fourier, 8, null, [1, .5, .25, .125], true);
	populate(fn.fourier, 8, [1, .5, .25, .125], null, true);
	t.end()
});


t('noise', t => {
	draw(fn.noise)
	t.end()
})

t('clausen', t => {
	draw(fn.clausen)
	var clausen = populate(fn.clausen, 10);
	t.ok(almost(clausen[5], 0))
	t.equal(fn.clausen(-.75), fn.clausen(.25))
	t.end()
});

t('interpolate', t => {
	let set = Array.from({length: 6}, (v, i) => Math.random()*2 - 1)
	draw(fn.interpolate, set)

	var int = populate(fn.interpolate, 10, [0, .5, 1, .5, 0]);
	t.equal(int[0], 0)
	t.equal(int[1], 0.25)
	t.equal(int[2], 0.5)
	t.equal(int[9], 0)

	t.end()
})

t('step', t => {
	let set = Array.from({length: 6}, (v, i) => Math.random()*2 - 1)
	draw(fn.step, set)
	t.end()
})