# Theory Value

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theory Value
imports Type
begin

    (*  Title:      HOL/Bali/Value.thy
        ID:         $Id: Value.thy,v 1.7 2005/08/28 14:04:44 wenzelm Exp $
        Author:     David von Oheimb
    *)
    header {* Java values *}

    theory Value imports Type begin

    typedecl loc            --{* locations, i.e. abstract references on objects *}

    datatype val
            = Unit          --{* dummy result value of void methods *}
            | Bool bool     --{* Boolean value *}
            | Intg int      --{* integer value *}
            | Null          --{* null reference *}
            | Addr loc      --{* addresses, i.e. locations of objects *}

    translations "val" <= (type) "Term.val"
                 "loc" <= (type) "Term.loc"

    consts   the_Bool   :: "val => bool"
    primrec "the_Bool (Bool b) = b"
    consts   the_Intg   :: "val => int"
    primrec "the_Intg (Intg i) = i"
    consts   the_Addr   :: "val => loc"
    primrec "the_Addr (Addr a) = a"

    types   dyn_ty      = "loc => ty option"
    consts
      typeof        :: "dyn_ty => val => ty option"
      defpval       :: "prim_ty => val"  --{* default value for primitive types *}
      default_val   :: "     ty => val"  --{* default value for all types *}

    primrec "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 Void    = Unit"
            "defpval Boolean = Bool False"
            "defpval Integer = Intg 0"
    primrec "default_val (PrimT pt) = defpval pt"
            "default_val (RefT  r ) = Null"

    end