interpretStmts ((SDecl decls):restStms) = do env_exp <- iDecl decls restStms
                                             return $ snd env_exp
interpretStmts ((SDecl decls):restStms) = do env_exp <- iDecl decls restStms
                                             return $ snd env_exp
interpretStmts ((SDecl decls):restStms) = do env_exp <- iDecl decls restStms
                                             return $ snd env_exp