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lib/PhpSpreadsheet/Calculation/Engine/CyclicReferenceStack.php

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+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Engine;
+
+class CyclicReferenceStack
+{
+    /**
+     * The call stack for calculated cells.
+     *
+     * @var mixed[]
+     */
+    private array $stack = [];
+
+    /**
+     * Return the number of entries on the stack.
+     */
+    public function count(): int
+    {
+        return count($this->stack);
+    }
+
+    /**
+     * Push a new entry onto the stack.
+     */
+    public function push(mixed $value): void
+    {
+        $this->stack[$value] = $value;
+    }
+
+    /**
+     * Pop the last entry from the stack.
+     */
+    public function pop(): mixed
+    {
+        return array_pop($this->stack);
+    }
+
+    /**
+     * Test to see if a specified entry exists on the stack.
+     *
+     * @param mixed $value The value to test
+     */
+    public function onStack(mixed $value): bool
+    {
+        return isset($this->stack[$value]);
+    }
+
+    /**
+     * Clear the stack.
+     */
+    public function clear(): void
+    {
+        $this->stack = [];
+    }
+
+    /**
+     * Return an array of all entries on the stack.
+     *
+     * @return mixed[]
+     */
+    public function showStack(): array
+    {
+        return $this->stack;
+    }
+}