diff --git a/interp.py b/interp.py
index 606c082..f57cfc8 100644
--- a/interp.py
+++ b/interp.py
@@ -24,45 +24,50 @@
     def verb_Read(self, args):
         return Text(input())
 
-def resolve_value(env, value):
-    if value.__class__ == ast_types.Reference:
-        return env[value.value]
-    elif value.__class__ == ast_types.Text:
-        return Text(value.value)
-    else:
-        print("Unimplemented value: %s" % (value))
+class Interpreter:
+    def resolve_value(self, env, value):
+        if value.__class__ == ast_types.Reference:
+            return env[value.value]
+        elif value.__class__ == ast_types.Text:
+            return Text(value.value)
+        else:
+            print("Unimplemented value: %s" % (value))
 
-def run_statement(env, ast):
-    subject = resolve_value(env, ast.subject)
-    if ast.verb == None:
-        return subject
-    args = []
-    for arg in ast.arguments:
-        args.append(resolve_value(env, arg))
-    return getattr(subject, "verb_" + ast.verb)(args)
+    def run_statement(self, env, ast):
+        subject = self.resolve_value(env, ast.subject)
+        if ast.verb == None:
+            return subject
+        args = []
+        for arg in ast.arguments:
+            args.append(self.resolve_value(env, arg))
+        return getattr(subject, "verb_" + ast.verb)(args)
 
-def run_set(env, ast):
-    env[ast.subject] = run_statement(env, ast.statement)
-    return env[ast.subject]
+    def run_set(self, env, ast):
+        env[ast.subject] = self.run_statement(env, ast.statement)
+        return env[ast.subject]
 
-def run_conditional(env, ast):
-    print("Unimplemented if")
-    return None
+    def run_conditional(self, env, ast):
+        print("Unimplemented if")
+        return None
 
-def run_command(env, ast):
-    if ast.__class__ == ast_types.Statement:
-        return run_statement(env, ast)
-    elif ast.__class__ == ast_types.Set:
-        return run_set(env, ast)
-    elif ast.__class__ == ast_types.Conditional:
-        return run_conditional(env, ast)
-    else:
-        print("Unknown command %s" % (ast))
+    def run_command(self, env, ast):
+        if ast.__class__ == ast_types.Statement:
+            return self.run_statement(env, ast)
+        elif ast.__class__ == ast_types.Set:
+            return self.run_set(env, ast)
+        elif ast.__class__ == ast_types.Conditional:
+            return self.run_conditional(env, ast)
+        else:
+            print("Unknown command %s" % (ast))
+            return None
+
+    def run(self, env, ast):
+        for command in ast:
+            self.run_command(env, command)
         return None
 
 def run_ast(ast):
     env = {
         "System": Module_System(),
     }
-    for command in ast:
-        run_command(env, command)
+    return Interpreter().run(env, ast)