add pattern Interpreter

Behavioral/Interpreter/Context.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types=1);
+
+namespace DesignPatterns\Behavioral\Interpreter;
+
+use Exception;
+
+class Context
+{
+    private array $poolVariable;
+
+    public function lookUp(string $name): bool
+    {
+        if (!key_exists($name, $this->poolVariable)) {
+            throw new Exception("no exist variable: $name");
+        }
+
+        return $this->poolVariable[$name];
+    }
+
+    public function assign(VariableExp $variable, bool $val)
+    {
+        $this->poolVariable[$variable->getName()] = $val;
+    }
+}