(* Title: HOL/Bali/Value.thy
Author: David von Oheimb
*)
subsection \<open>Java values\<close>
theory Value imports Type begin
typedecl loc \<comment>\<open>locations, i.e. abstract references on objects\<close>
datatype val
= Unit \<comment>\<open>dummy result value of void methods\<close>
| Bool bool \<comment>\<open>Boolean value\<close>
| Intg int \<comment>\<open>integer value\<close>
| Null \<comment>\<open>null reference\<close>
| Addr loc \<comment>\<open>addresses, i.e. locations of objects\<close>
primrec the_Bool :: "val \<Rightarrow> bool"
where "the_Bool (Bool b) = b"
primrec the_Intg :: "val \<Rightarrow> int"
where "the_Intg (Intg i) = i"
primrec the_Addr :: "val \<Rightarrow> loc"
where "the_Addr (Addr a) = a"
type_synonym dyn_ty = "loc \<Rightarrow> ty option"
primrec typeof :: "dyn_ty \<Rightarrow> val \<Rightarrow> ty option"
where
"typeof dt Unit = Some (PrimT Void)"
| "typeof dt (Bool b) = Some (PrimT Boolean)"
| "typeof dt (Intg i) = Some (PrimT Integer)"
| "typeof dt Null = Some NT"
| "typeof dt (Addr a) = dt a"
primrec defpval :: "prim_ty \<Rightarrow> val" \<comment>\<open>default value for primitive types\<close>
where
"defpval Void = Unit"
| "defpval Boolean = Bool False"
| "defpval Integer = Intg 0"
primrec default_val :: "ty \<Rightarrow> val" \<comment>\<open>default value for all types\<close>
where
"default_val (PrimT pt) = defpval pt"
| "default_val (RefT r ) = Null"
end