OpenEuphoria

Re: object(x) rethink

• Posted by Igor Kachan <kinz at pete??ink.ru> Mar 02, 2008
• 891 views

jacques deschênes wrote:
 
> I think you completely miss the point with generic type.
> There is no point testing if a variable is of type 'object' as all variables
> hold an object.
> The object data type is there as a generic container and as is, it is very
> usefull.
> It is right to say that it is useless to write something like:
> 
> if object(x) then...
> 
> But for the coherance of the language this must be a valid declaration and
> must
> behave like any other datatype validation.
> There is nothing to change in the language here. All language that use generic
> type behave the same way.
> In OOP for exemple there is alway a generic class from which all other classes
> are derived and if you test any class to know if it is of that generic the
> answer
> will allways be TRUE, like in euphoria.
> This coherent in syntax and in semantic.

Ok, I've prepared some code, to be more concrete and clear.
Try it please:

type old_object(object x)
   return object(x)
end type   

global type object(old_object x)
    if integer(x) then return 1
      elsif atom(x) then return 2
    elsif sequence(x) then return 3
      else return 4 -- reserved for variables, declared with type 'object'
    end if
end type

sequence s
    s={1,1}
   ? object(s) -- true, 3
integer i
    i=1
   ? object(i) -- true, 1
atom a
     a=2.5
   ? object(a) -- true, 2
object x
     x = {}
   ? object(x) -- true, 3 or 2 or 1 now
               -- but must be 4, I think

The "object" word is ambiguous in EU, I think.
It is some piece of data in common sence, so to say,
and it is some very specific type of variable.
This new type in above code seems to have both
meanings, I think.
But that old one - it is just useless, yes,
you are right.

Regards,
Igor Kachan
kinz at peterlink.ru