typelevel/spire

Eq[Polynomial[C]] throws ArrayIndexOutOfBoundsException for negative exponents

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#756 opened on Jan 9, 2019

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 (7 comments) (0 reactions) (0 assignees)Scala (238 forks)batch import
good first issue

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Description

Reproduce:

scala> def x: Polynomial[Int] = PolySparse(List(Term(-1642198702, -1)))
x: spire.math.Polynomial[Int]
scala> x === x
java.lang.ArrayIndexOutOfBoundsException: -1
  at scala.runtime.ScalaRunTime$.array_update(ScalaRunTime.scala:76)
  at spire.math.poly.PolySparse.coeffsArray(PolySparse.scala:54)
  at spire.math.PolynomialEq.eqv(Polynomial.scala:556)
  at spire.math.PolynomialEq.eqv$(Polynomial.scala:555)
  at spire.math.PolynomialInstances0$$anon$14.eqv(Polynomial.scala:568)
  ... 36 elided

Contributor guide

Research direction
Investigate the `coeffsArray` method in `PolySparse.scala` to ensure it handles negative exponents without causing an `ArrayIndexOutOfBoundsException`. The fix likely involves adjusting array indexing or filtering out negative exponents before array access.
Tech stack
scala
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Scalasbt
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75