josdejong/mathjs

Incompatibility between `number: bigint` and high-precision floating point arithmetic

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#3,539 opened on Sep 25, 2025

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Description

with math.js 14.6.0

math.config({
  number: "bigint", 
  precision: 998,
  relTol: 1e-320,
  absTol: 1e-323,
  numberFallback: "BigNumber"
});

outch, a part of the code doing stuff like :

  • math.log10( 0n ) (which before was containing bignumbers) returns errors now "i.toNumber is not a function"
  • math.log( 123n ) returns now 4.812184355372417 , before it was returning a bignumber of 998 digits
  • floor(log10(( 1n ))) returns now "Number of decimals in function round must be an integer from 0 to 15 inclusive"

I was parsing big integers as bignumber to return long primes and now I get messages like this "Cannot mix BigInt and other types, use explicit conversions"

the price to pay in code update seems very high , and all calculations based on logarithms no longer return the configuration's precision. every constant are now limited to few digits math.pi = 3.141592653589793.

Originally posted by @nycos62 in https://github.com/josdejong/mathjs/discussions/3533#discussioncomment-14504003

These are all bugs; it should be possible to conveniently perform high-precision floating-point arithmetic when (perhaps especially when) numbers default to bigints.

Contributor guide

Research direction
Investigate how math.js handles bigint numbers in high precision mode. Trace the code paths for `log10`, `log`, `floor`, and constants like `pi` when `number: 'bigint'` is set. Ensure that falling back to BigNumber works correctly for all arithmetic and functions. Check the config options `numberFallback` and `precision` interactions.
Tech stack
javascript
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
JavaScriptmath.js
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50