Module ListHead.

Lemma wand_frame_intro_list_head: forall sh (x y: int) (s: list int) (l: val),
listrep sh (x :: s) l |--
field_at sh t_struct_list [StructField _head] (Vint x) l *
(field_at sh t_struct_list [StructField _head] (Vint y) l -* listrep sh (y :: s) l).