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Equality of dbObjects

tweeks

Are dbobjects ever equal?

I did a test, creating two labels that are exact copies of eachother: same lpp, same xy, etc. Watch what happens:

> forall(prop label1->? get(label1 prop) == get(label2 prop))
 t
> label1 == label2 
 nil 


Looks like equality is not implemented for labels?
Parents

  •  You can already overload the builtin operators within a SKILL++ lexical scope by defining a function with the same name. For example, see this code example (put in a file with a .ils suffix before loading)

    let((a)
     flet(((arrayref (arr ind) arr[ind] || (arr[ind]=makeTable('tab nil))))

      a=makeTable('tab nil)
      a["hello"]["world"]["andrew"]=123
     )
    )

    defmacro(WithAutoHash (@rest body)
     `flet(((arrayref (arr ind) arr[ind] || (arr[ind]=makeTable('tab nil))))
       ,@body
      )
    )

    procedure(TrExampleArray()
      let(((arr makeTable('tab nil)))
        WithAutoHash(
          arr["my"]["big"]["test"]=7
          arr["my"]["other"]["test"]=9
          arr
        )
      )
    )

    This example defines a macro, WithAutoHash, within which it redefines the meaning of arrayref to behave differently - to automatically define an array if an unused index is used. You could do a similar thing with equal (without the macro), using an object oriented approach to define relevant methods (use toplevel('ils) if pasting in the CIW, or a .ils suffix if in a file):

    defgeneric(myEqual (obj1 obj2)
      obj1==obj2
    )

    defmethod(myEqual ((obj1 dbobject) (obj2 dbobject))
      ; do your comparison (return t for now for illustration)
      t
    )

    ; overrride == within the lexical scope defined by the let
    let(((equal myEqual))
      printf("Equality test %L\n" dbObj1==dbObj2)
    )

    Regards,

    Andrew

Reply

  •  You can already overload the builtin operators within a SKILL++ lexical scope by defining a function with the same name. For example, see this code example (put in a file with a .ils suffix before loading)

    let((a)
     flet(((arrayref (arr ind) arr[ind] || (arr[ind]=makeTable('tab nil))))

      a=makeTable('tab nil)
      a["hello"]["world"]["andrew"]=123
     )
    )

    defmacro(WithAutoHash (@rest body)
     `flet(((arrayref (arr ind) arr[ind] || (arr[ind]=makeTable('tab nil))))
       ,@body
      )
    )

    procedure(TrExampleArray()
      let(((arr makeTable('tab nil)))
        WithAutoHash(
          arr["my"]["big"]["test"]=7
          arr["my"]["other"]["test"]=9
          arr
        )
      )
    )

    This example defines a macro, WithAutoHash, within which it redefines the meaning of arrayref to behave differently - to automatically define an array if an unused index is used. You could do a similar thing with equal (without the macro), using an object oriented approach to define relevant methods (use toplevel('ils) if pasting in the CIW, or a .ils suffix if in a file):

    defgeneric(myEqual (obj1 obj2)
      obj1==obj2
    )

    defmethod(myEqual ((obj1 dbobject) (obj2 dbobject))
      ; do your comparison (return t for now for illustration)
      t
    )

    ; overrride == within the lexical scope defined by the let
    let(((equal myEqual))
      printf("Equality test %L\n" dbObj1==dbObj2)
    )

    Regards,

    Andrew

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