OpenEuphoria

Re: object(x) rethink

• Posted by Bill Reed <rpfproeu at ai?.?om> Mar 02, 2008
• 756 views

Igor Kachan wrote:
> 
> Bill Reed wrote:
>  
> > 
> > object useless????
> > 
> > ----------------------------------------------------------------------
> > A variable must be declared as an object in order to determine what
> > type it is.
> > 
> >   object x
> >   
> >   if sequence(x) then
> >     puts(1, "variable is a sequence")
> >   end if
> >   
> >   if integer(x)
> >     puts(1, "variable is an integer")
> >   end if
> >   
> > ----------------------------------------------  
> >   doeumentation for gets() from library.doc
> > ----------------------------------------------
> >   
> > 
> > Example 1:
> > 
> >               sequence buffer
> >               object line
> >               integer fn
> >               
> >               -- read a text file into a sequence
> >               fn = open("myfile.txt", "r")
> >               if fn = -1 then
> >                   puts(1, "Couldn't open myfile.txt\n")
> >                   abort(1)
> >               end if
> >               
> >               buffer = {}
> >               while 1 do
> >                   line = gets(fn)
> >                   if atom(line) then
> >                       exit   -- -1 is returned at end of file
> >                   end if
> >                   buffer = append(buffer, line)
> >               end while
> 
> Hi Bill,
> 
> Try please:
> }}}
<eucode>
> integer i   i= 1
> atom a      a= 2
> sequence s  s={3}
> object x    x={4,{5}}
> 
> if object(i) then ? i end if
> if object(a) then ? a end if
> if object(s) then ? s end if
> if object(x) then ? x end if
> </eucode>
{{{

> 
> Is *object()*, not *object*, useful?
> 
> This *object()* is just a dummy function now.
> It stands just for some 'symmetry' with integer(),
> atom() and sequence() functions.
> 
> Do you see now?
> 
> Regards,
> Igor Kachan
> kinz at peterlink.ru


Sure, integer, atom, and sequences are *objects*, 
but not all objects are sequences, and 
not all objects are atoms and 
not all objects are integers.

I don't check for "if object(x)" or "if not object(x)"

If I declare an object as a sequence, and one time it becomes an an integer,
I get a "type_check failure".  I can assign anything to an object, but I
can't assign an integer to a sequence.

  object x

  x = "abc"      -- ok
  x = -1         -- ok

But:

  sequence x
  
  x = "abc"       -- ok
  x = -1          -- type_check error, x is -1

To fix:

  object o
  sequence s
  integer i
  atom a

  o = "abc"
  o = -1
  o = 5.3

  if sequence(o) then
    s = o
  elsif integer(o) then
    i = o
  elsif atom(o) then
    a = o
  end if

Bill