josdejong/mathjs

Nested derivatives fail

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#3528 opened on Sep 8, 2025

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

Description

Describe the bug mathJs evaluates this derivative correctly: derivative('x * e^x', "x") // returns "e ^ x * (x + 1)"

however, if the expression to be differentiated is involves another derivative mathJs returns an incorrect answer: derivative('x * derivative("e^x", "x")', "x") // returns "e^x"

To Reproduce enter expression in mathJs demo window: derivative('x * derivative("e^x", "x")', "x")

Contributor guide

Tech stack
javascript
Domain
data
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.
1-3 hours
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
JavaScriptbasic calculus
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The bug occurs when the derivative function is called inside another derivative expression. Look at the implementation of math.derivative in the source code (likely in src/expression/function/derivative.js). Investigate how nested function calls are parsed and evaluated. The issue may be in how the derivative handles its internal expression scope or symbolic differentiation of derivative calls. Check recent commits or issues for related discussions.