# Theory Value

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theory Value
imports Type
begin

    (*  Title:      HOL/MicroJava/J/Value.thy
        ID:         $Id: Value.thy,v 1.11 2005/06/17 14:13:09 haftmann Exp $
        Author:     David von Oheimb
        Copyright   1999 Technische Universitaet Muenchen
    *)

    header {* \isaheader{Java Values} *}

    theory Value imports Type begin

    typedecl loc_ -- "locations, i.e. abstract references on objects"

    datatype loc
      = XcptRef xcpt -- "special locations for pre-allocated system exceptions"
      | Loc loc_     -- "usual locations (references on objects)"

    datatype val
      = Unit        -- "dummy result value of void methods"
      | Null        -- "null reference"
      | Bool bool   -- "Boolean value"
      | Intg int    -- "integer value, name Intg instead of Int because
                       of clash with HOL/Set.thy"
      | Addr loc    -- "addresses, i.e. locations of objects "

    consts
      the_Bool :: "val => bool"
      the_Intg :: "val => int"
      the_Addr :: "val => loc"

    primrec
      "the_Bool (Bool b) = b"

    primrec
      "the_Intg (Intg i) = i"

    primrec
      "the_Addr (Addr a) = a"

    consts
      defpval :: "prim_ty => val"  -- "default value for primitive types"
      default_val :: "ty => val"   -- "default value for all types"

    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