From 0bf33a4fc13474835414a24c80d50cc7710eaf49 Mon Sep 17 00:00:00 2001
From: aherbert <aherbert@apache.org>
Date: Fri, 15 Jul 2022 17:28:33 +0100
Subject: [PATCH] Use Complex.ZERO.

This does not change the equals comparison. Note that this will not
detect sign differences, e.g. (0.0, 0.0) == (-0.0, 0.0) and a tolerance
may be required for more robustness.
---
 .../commons/math4/legacy/analysis/solvers/LaguerreSolver.java  | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/analysis/solvers/LaguerreSolver.java b/commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/analysis/solvers/LaguerreSolver.java
index e0dcc37b7..24afe0b7f 100644
--- a/commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/analysis/solvers/LaguerreSolver.java
+++ b/commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/analysis/solvers/LaguerreSolver.java
@@ -368,7 +368,8 @@ public class LaguerreSolver extends AbstractPolynomialSolver {
                 final Complex denominator = dplus.abs() > dminus.abs() ? dplus : dminus;
                 // Perturb z if denominator is zero, for instance,
                 // p(x) = x^3 + 1, z = 0.
-                if (denominator.equals(Complex.ofCartesian(0.0, 0.0))) {
+                // This uses exact equality to zero. A tolerance may be required here.
+                if (denominator.equals(Complex.ZERO)) {
                     z = z.add(Complex.ofCartesian(absoluteAccuracy, absoluteAccuracy));
                     oldz = Complex.ofCartesian(Double.POSITIVE_INFINITY,
                                        Double.POSITIVE_INFINITY);