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Arbitrary precision rational number arithmetic

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var rat = require('big-rat')
//Construct a pair of rational numbers; 
//   a = 1/10 
//   b = 2/10 
var a = rat(1, 10)
var b = rat(2, 10)
//Compute their sum 
var add = require('big-rat/add')
var c = add(a, b)
//Print out sum 
var toString = require('big-rat/to-string')
console.log('a+b=', toString(c))
//And also convert to a number 
var toFloat = require('big-rat/to-float')
console.log('exact rational result:', toFloat(c))
//For comparison, here is the same computation performed with floats 
var x = 0.1
var y = 0.2
console.log('approximate float result:', x + y)


a+b= 3/10
exact rational result: 0.3
approximate float result: 0.30000000000000004


npm i big-rat


var r = require('big-rat')(n[, d])

Constructs a rational number as the quotient n/d

  • n is the numerator. Can be a float, string, bignum or rational
  • d is the denominator (optional, default 1)

Returns A rational number

var f = require('big-rat/to-float')(r)

Returns The closest floating point number to r

var s = require('big-rat/to-string')(r)

Returns A string representing the big rat r

var b = require('big-rat/is-rat')(r)

Returns true if r is a big rat

var c = require('big-rat/add')(a, b)

Returns a+b

var c = require('big-rat/sub')(a, b)

Returns a-b

var c = require('big-rat/mul')(a, b)

Returns a*b

var c = require('big-rat/div')(a, b)

Returns a/b

var c = require('big-rat/neg')(a)

Returns -a

var c = require('big-rat/recip')(a)

Returns 1/a

var c = require('big-rat/sign')(a)

Returns One of the following values:

  • -1 if a<0
  • 0 if a=0
  • +1 if a>0

var c = require('big-rat/abs')(a)

Returns |a|

var c = require('big-rat/min')(a, b)

Returns min(a,b)

var c = require('big-rat/max')(a, b)

Returns max(a,b)

var c = require('big-rat/equals')(a, b)

Returns true if a=b, false otherwise

var c = require('big-rat/cmp')(a, b)


  • -1 if a<b
  • 0 if a=b
  • +1 if a>b


(c) 2015 MIT License