It shall be a class C misdemeanor for any person to act as a guard or lookout for any building, premises, or establishment used for gambling, for illegal sale or purchase of intoxicating liquors, or for any person soliciting, offering or engaging in prostitution, gambling or any other form of vice, or illegal act, or any prostitute, on any street or sidewalk. Nor shall any person give any signal intended to, or calculated to warn, or give warning of the approach of any peace officer to any person in or about such building or premises or place mentioned herein-. (Code 1975 § 13-340)