complexjs

complexjs

This is a library for complex numbers calculations in javascript using plain objects immutably.

It has been designed to be used for geometry applications, for which a little API has been included.

Complex numbers API

Any object with the properties re or im (or r and arg) qualifies as a complex number for this API, so there are no creation methods for them.

Function	Explanation
csum(c0 : complex, c1: complex)	Returns c0 plus c1
csub(c0 : complex, c1: complex)	Returns the c0 minus c1
cmul(c0 : complex, c1: complex)	Returns c0 times c1
cdiv(c0 : complex, c1: complex)	Returns c0 over c1
conjugate(c : complex)	Returns the conjugate of c
cmod(c : complex)	Returns the modulus of c
cmod2(c : complex)	Returns the square modulus of c
isCartesian(c : complex)	Returns true if c is can behave as a cartesian complex number
isPolar(c : complex)	Returns true if c is can behave as a polar complex number
re(c : complex)	Returns the real part of c
im(c : complex)	Returns the imaginary part of c
r(c : complex)	Returns the modulus of c
arg(c : complex)	Returns the argument of c
cequals(c0 : complex, c1: complex)	Returns true if c0 and c1 are equal

Geometry API

Function	Explanation
vector(x : number, y : number)	Returns a plain object such as {re: x, im: y}
distance(c0 : complex, c1: complex)	Returns the euclidian distance between c0 and c1
translate(c : complex, translation : complex)	Translates c by summing translation
rotate(c : complex, delta : number, pivot = {re: 0, im: 0})	Rotates c around pivot for delta radians
scale(c : complex, factor : number, pivot = {re: 0, im: 0})	Scales c from pivot multiplying by factor

Complex number calculations examples

Creating a complex number is as simple as:

// Cartesian form
const c_cartesian = {
  re: 1,
  im; 0
};

// Polar form
const c_polar = {
  r: 1,
  arg: Math.PI / 2
};

Both forms can be mixed, and the form of the first number will be preserved:

csum(c_cartesian, c_polar); // => {re: 1, im: 1}
csum(c_polar, c_cartesian); // => {r: 1.414, arg: 0.785}

All the basic functions are provided. All of them are pure functions:

cmul(c_cartesian, c_polar); // => {re: 0, im: 1}
cdiv(c_cartesian, c_polar); // => {re: 0, im: -1}
cmod(c_cartesian); // => 1
conjugate(c_polar); // => {r: 1, arg: - 1.5707}

Using plain objects

The API is designed so that any object can be passed to the functions, and any property other than re and im (or r and arg) will remain unchanged. This can be useful to compose plain objects.

const c_object = {
  rgb: [255, 255, 255],
  re: 1,
  im: 1
};

const c_number = {
  re: 5,
  im: -1
};

csum(c_object, c_number) // => {rgb: [255, 255, 255], re: 6, im: 0}

In case both objects have properties, they will be merged. The first parameter will override the second one if the have a property with the same name.

Geometry applications examples

Complex numbers serve as an elegant representation of 2d geometry. To make its use even simpler, some methods have been created to wrap the algebra to match its geometric meaning.

vector(1, 2) // => {re: 1, im: 2}

const square = [
  vector(0, 0),
  vector(1, 0),
  vector(1, 1),
  vector(0, 1)
];

const scaledSquare = square.map(c => scale(c, 2));
const translatedSquare = scaledSquare.map(c => translate(c, vector(-1, -1)));
const rotatedSquare = translatedSquare.map(c => rotate(c, Math.PI / 2));

// => [
//   vector(1, -1),
//   vector(1, 1),
//   vector(-1, 1),
//   vector(-1, -1)
// ];