Edit detail for SandBox Object revision 1 of 2

Type-safe Objects in SPAD

)abbrev domain OBJ Object

Object(C:Type): CoercibleTo(OutputForm) with
        Type            : % -> C
        new             : (SExpression, None) -> %
        dom             : % -> SExpression
        obj             : % -> None

        if C has BasicType then
          BasicType
        if C has Ring then
          _+            : (%,%) -> %

 == add

     Rep == Record(dm: SExpression, ob: None)
     import Rep

     dom(x:%):SExpression     == (x pretend Rep).dm

     obj(x:%):None            == (x pretend Rep).ob

     Type(x:%):C              == dom(x) pretend C

     if C has BasicType then
       _=(x:%,y:%):Boolean      == 
         xR := x pretend Rep
         yR := y pretend Rep
         if xR.dm = yR.dm then
             D:BasicType := xR.dm pretend BasicType
             X:D := (obj x) pretend D
             Y:D := (obj y) pretend D
             (X=Y)$D
         else false

     if C has Ring then
       _+(x:%,y:%):% ==
         xR := x pretend Rep
         yR := y pretend Rep
         if xR.dm = yR.dm then
             D:= xR.dm pretend Ring
             X:D := (obj x) pretend D
             Y:D := (obj y) pretend D
             Z:= (X+Y)$D
             new(xR.dm,Z pretend None)
         else error "not possible"

     coerce(x):OutputForm ==
       xR := x pretend Rep
       obj1 : OutputForm :=
         spad2BootCoerce(xR.ob, xR.dm,
            list("OutputForm"::Symbol)$List(Symbol))$Lisp
       dom1 :=
         p:Symbol := prefix2String(xR.dm)$Lisp
         atom?(p pretend SExpression) => list(p)$List(Symbol)
         list(p)$Symbol
       hconcat cons(obj1, cons(":"::OutputForm, [a::OutputForm for a in dom1]))

     new(domain:SExpression, object:None):% ==
       (isValidType(domain)$Lisp)@Boolean => construct(domain, object)$Rep pretend %
       domains := devaluate(domain)$Lisp
       (isValidType(domains)$Lisp)@Boolean => construct(domains, object)$Rep pretend %
       error "must have a valid domain as first argument"

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/2739318749442070762-25px001.spad
      using old system compiler.
   OBJ abbreviates domain Object 
------------------------------------------------------------------------
   initializing NRLIB OBJ for Object 
   compiling into NRLIB OBJ 
************* USER ERROR **********
available signatures for Rep: 
    NONE
NEED Rep: () -> ?
****** comp fails at level 1 with expression: ******
((DEF (|Rep|) (NIL) (NIL)
  (|Record| (|:| |dm| (|SExpression|)) (|:| |ob| (|None|)))))
****** level 1  ******
$x:= (DEF (Rep) (NIL) (NIL) (Record (: dm (SExpression)) (: ob (None))))
$m:= $EmptyMode
$f:=
((((|$Information| #) (|$DomainsInScope| # # #) (|coerce| #) (~= #) ...)))

   >> Apparent user error:
   unspecified error

)abbrev package HAS Has

Has(C:Type,S:C): with
        coerce      : S         -> Object(C)
        avail       : Object(C) -> Union(S, "failed")
        is?         : Object(C) -> Boolean
        get         : Object(C) -> S

    == add

        Sexpr:SExpression := devaluate(S)$Lisp

        is?(a:Object(C)):Boolean  == dom(a) = Sexpr

        coerce(s:S):Object(C) == new(Sexpr, s pretend None)

        avail(a:Object(C)):Union(S,"failed") ==
            is? a => obj(a) pretend S
            "failed"

        get(a:Object(C)):S ==
            is? a => obj(a) pretend S
            error "Cannot retract value."

   Compiling FriCAS source code from file 
      /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/6566032851093813704-25px002.spad
      using old system compiler.
   HAS abbreviates package Has 
------------------------------------------------------------------------
   initializing NRLIB HAS for Has 
   compiling into NRLIB HAS 
****** Domain: C already in scope
   compiling exported is? : Object C -> Boolean
   Semantic Errors: 
      [1]  Object is not a known type

   Warnings: 
      [1] is?:  dom has no value

****** comp fails at level 2 with expression: ******
error in function is? 

(= | << | (|dom| |a|) | >> | |Sexpr|)
****** level 2  ******
$x:= (dom a)
$m:= $EmptyMode
$f:=
((((|a| # #) (|Sexpr| # #) (|#| #) (= #) ...)))

   >> Apparent user error:
   cannot compile (dom a)

)sh Object(SetCategory)

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?

)sh Object(Ring)

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?

)sh Has

 Has  is a package constructor
 Abbreviation for Has is HAS 
 This constructor is not exposed in this frame.
------------------------------- Operations --------------------------------

   >> System error:
   The function BOOT::|Has| is undefined.

b:Object(BasicType):="abc"

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?
a:=[1,"xxx",1.2]::List Object SetCategory

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?
a.1

   There are no library operations named a 
      Use HyperDoc Browse or issue
                                 )what op a
      to learn if there is any operation containing " a " in its name.

   Cannot find a definition or applicable library operation named a 
      with argument type(s) 
                               PositiveInteger

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.
a.2

   There are no library operations named a 
      Use HyperDoc Browse or issue
                                 )what op a
      to learn if there is any operation containing " a " in its name.

   Cannot find a definition or applicable library operation named a 
      with argument type(s) 
                               PositiveInteger

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.
Type(a.2)

   There are no library operations named a 
      Use HyperDoc Browse or issue
                                 )what op a
      to learn if there is any operation containing " a " in its name.

   Cannot find a definition or applicable library operation named a 
      with argument type(s) 
                               PositiveInteger

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.
(a.1 = a.2)$Object(SetCategory)

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?
is?(a.2)$Has(SetCategory,String)

   Has is an unknown constructor and so is unavailable. Did you mean to
      use -> but type something different instead?
get(a.2)@String

   There are no library operations named a 
      Use HyperDoc Browse or issue
                                 )what op a
      to learn if there is any operation containing " a " in its name.

   Cannot find a definition or applicable library operation named a 
      with argument type(s) 
                               PositiveInteger

      Perhaps you should use "@" to indicate the required return type, 
      or "$" to specify which version of the function you need.
avail(a.3)$Has(SetCategory,Float)

   Has is an unknown constructor and so is unavailable. Did you mean to
      use -> but type something different instead?
avail(a.2)$Has(SetCategory,Float)

   Has is an unknown constructor and so is unavailable. Did you mean to
      use -> but type something different instead?
avail(a.1)$Has(SetCategory,Float) case Float

   Has is an unknown constructor and so is unavailable. Did you mean to
      use -> but type something different instead?

n:Object(Ring)

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?
n:=coerce(1)$Has(Ring,Integer)

   Has is an unknown constructor and so is unavailable. Did you mean to
      use -> but type something different instead?
m:Object(Ring):=coerce(2)$Has(Ring,Integer)

   Object is an unknown constructor and so is unavailable. Did you mean
      to use -> but type something different instead?
n+m

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