momenta

momentum

Basic vector operations over the rational numbers.

Support

Examples

where m.r is the rationals used by momentum

var m = require('momentum');
m([1])[0] === m.r(1); // true

while in the case of rationals it made sense to keep direct equality between the created objects, I think this is not the case with momentumi. However this might change some time in the future.

Another issue is that no matter how much I wish, there isn't a good, widely supported way to subclass array (not until es6 is widely supported). The workarounds available kinda create more problems than they solve, so after a day of thinking I went in the minimalist direction. This also means, that while momentum methods expect arrays and scalars with add, sub, scale, disperse, dot methods on them, the module's user should provide these methods.

Probably worth to mention that the API gives you easy solution to this:

var m = require('momentum');
var equal = require('deep-equal');
var r = m.r;
equal(m.disperse(m([1,4,7,9,16]), r(12)), m([r(1,12),r(1,3),r(7,12),r(3,4),r(4,3)])); // true

API

all methods on momentum objects will return an array of rationals with the exception of .dot, which will return a single rational

Casting an array of integers to rationals

momentum()

m([3])[0].toString()  // 3/1

Casting an integer to a rational

momentum.r()

m.r(5).toString()  // 5/1

Scaling up

scale

m.scale(m([1,3,5]), m.r(7))  // [7/1,21/1,35/1]

Scaling down

disperse

m.disperse(m([1,3,5]), m.r(9)) // [1/9,1/3,5/9]

Addition

add

m.add(m([1,3,5]), m([2,4,6])) // [3/1,7/1,11/1]

Subtraction

sub

m.sub(m([3,7,11]), m([2,4,6])) // [1/1,3/1,5/1]

Dot product

dot

m.dot(m([1,3,5]), m([7,11,13])) // 105/1

Cross product

cross

m.cross(m([1,3,5]), m([7,11,13])) // [-16/1, 22/1, -10/1]

Install

npm install momentum

You can use it in the browser with browserify