Define function wp, state wp_correctness

wp.v

@@ -291,3 +291,25 @@ Proof.
           unfold conseq_or_bottom in IHdeduction_m.
 Admitted.
 
+(***** Weakest precondition **************************************************)
+
+Fixpoint wp (instr: Instr) (cond: Assert) : Assert := match instr with
+| skip =>
+        cond
+| abort =>
+        assertTop
+| assign x expr =>
+        cond [[ x <- expr expr ]]
+| seq s1 s2 =>
+        wp s1 (wp s2 cond)
+| ifelse guard sIf sElse =>
+        (assertOfExpr guard -> wp sIf cond
+        /\ (~ (assertOfExpr guard) -> wp sElse cond)) % assert
+| while guard body => assertTop
+end.
+
+Theorem wp_correctness (instr: Instr) (post: Assert) :
+    ( |= [| wp instr post |] instr [| post |] ) % assert.
+Proof.
+    (* TODO *)
+Admitted.