josdejong/mathjs

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

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#3539 opened on Sep 25, 2025

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 (3 comments) (0 reactions) (0 assignees)JavaScript (13,832 stars) (1,298 forks)batch import
bughelp wanted

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

Tech stack
javascript
Domain
backenddata
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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.
needs investigation
Prerequisites
JavaScriptBigIntmathjs configurationhigh precision arithmetic
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the mathjs configuration for number: 'bigint' and how functions like log10, log, and floor interact with BigInt values. Review the source code in src/function/arithmetic/log10.js and src/function/arithmetic/log.js to understand how they handle different number types. Look at the discussion thread referenced (https://github.com/josdejong/mathjs/discussions/3533) for more context. Consider whether the issue stems from the conditional handling of BigInt vs BigNumber and how precision is applied. Check if there are existing tests for similar scenarios.