add do

bootstrap.php

@@ -22,5 +22,10 @@ function ml_get_lisp(): array
         return $results[count($results) - 1];
     });
 
+    $env->set('print', function (...$args) use ($printer) {
+        $printer->print($args);
+        return null;
+    });
+
     return [$lisp, $env];
 }

src/Evaller.php

@@ -60,6 +60,16 @@ class Evaller
 
                 $value = $this->doEval($ast->get(2), $env);
                 return $env->set($ast->get(1)->getName(), $value);
+            } elseif ($ast->get(0)->getName() == 'do') {
+                if ($ast->count() < 2) {
+                    throw new MadLispException("do requires at least 1 argument");
+                }
+
+                for ($i = 1; $i < $ast->count(); $i++) {
+                    $value = $this->evalAst($ast->get($i), $env);
+                }
+
+                return $value;
             } elseif ($ast->get(0)->getName() == 'if') {
                 if ($ast->count() < 3 || $ast->count() > 4) {
                     throw new MadLispException("if requires 2 or 3 arguments");