Theory Value

(*  Title:      Jinja/Common/Value.thy
    Author:     David von Oheimb, Tobias Nipkow
    Copyright   1999 Technische Universitaet Muenchen
*)

section ‹Jinja Values›

theory Value imports TypeRel begin

type_synonym addr = nat

datatype val
  = Unit        ― ‹dummy result value of void expressions›
  | Null        ― ‹null reference›
  | Bool bool   ― ‹Boolean value›
  | Intg int    ― ‹integer value› 
  | Addr addr   ― ‹addresses of objects in the heap›

primrec the_Intg :: "val ⇒ int" where
  "the_Intg (Intg i) = i"

primrec the_Addr :: "val ⇒ addr" where
  "the_Addr (Addr a) = a"

primrec default_val :: "ty ⇒ val"   ― ‹default value for all types› where
  "default_val Void      = Unit"
| "default_val Boolean   = Bool False"
| "default_val Integer   = Intg 0"
| "default_val NT        = Null"
| "default_val (Class C) = Null"

end