From 163c0f93eabcb3f6444220fbcdca5af8ea508cbd Mon Sep 17 00:00:00 2001
From: Sam <40273116+Aweptimum@users.noreply.github.com>
Date: Mon, 6 Nov 2023 10:36:47 -0600
Subject: [PATCH] Replace array_search with floating-point filter

array_search seems to fail in most cases when looking for a float in an array of floats. And even if it does find a match, if the key is 0, php evaluates `!0` to true.

To find a match, we can instead loop through and compare the numbers with `Arithmetic::almostEqual` and then explicitly check if `$key === false`
---
 src/LinearAlgebra/Eigenvector.php | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/LinearAlgebra/Eigenvector.php b/src/LinearAlgebra/Eigenvector.php
index abed66e87..de9c8de63 100644
--- a/src/LinearAlgebra/Eigenvector.php
+++ b/src/LinearAlgebra/Eigenvector.php
@@ -2,6 +2,7 @@
 
 namespace MathPHP\LinearAlgebra;
 
+use MathPHP\Arithmetic;
 use MathPHP\Exception;
 use MathPHP\Exception\MatrixException;
 use MathPHP\Functions\Map\Single;
@@ -66,8 +67,14 @@ public static function eigenvectors(NumericMatrix $A, array $eigenvalues = []):
         foreach ($eigenvalues as $eigenvalue) {
             // If this is a duplicate eigenvalue, and this is the second instance, the first
             // pass already found all the vectors.
-            $key = \array_search($eigenvalue, \array_column($solution_array, 'eigenvalue'));
-            if (!$key) {
+            $key = false;
+            foreach (\array_column($solution_array, 'eigenvalue') as $i => $v) {
+                if (Arithmetic::almostEqual($v, $eigenvalue, $A->getError())) {
+                    $key = $i;
+                    break;
+                }
+            }
+            if ($key === false) {
                 $Iλ = MatrixFactory::identity($number)->scalarMultiply($eigenvalue);
                 $T = $A->subtract($Iλ);