"Richard A. O'Keefe" <ok at atlas.otago.ac.nz> wrote:
> raymondasselin at sympatico.ca wrote:
> 	> >pt _ Point new.
> 	> >pt _ 25 at 125.
> 
> 	-There is lots of examples in Smalltalk which suggest something like
> 	Morph new, or Foo new, so for me this was not linked to the use of
> 	declaring the type of a variable.
> 	-I know that when you try to define new for a Class you defined, Squeak
> 	answer a caution 'new is used in the existing class system......' I
> 	usually ignore it and go forward. 
> 	
> 	Your remark is intriguing to me...did this means that it's not a good
> 	way to go to define a 'new' as a 'builder' Class method in Squeak ?
> 	I'm a little bit 'confus' because before your note I was pretty sure
> 	that pt_ Point new. was the way to go !!!
> 	
> John's point was that in
>     "1" pt _ Point new.
>     "2" pt _ 25 at 125.
> the first step is superfluous.  In optimising compiler terms, the value
> it constructs is "dead", it can never be used.  The code that creates a
> new Point has no side effects, so it doesn't accomplish anything useful
> to create a new point and then throw it away.  The second step does not
> modify the Point created in line "1", it constructs a whole new Point &
> just rebinds the variable pt.
> 
> #new is indeed the usual selector for creating new objects.
> It's not the only one.  In this case,
> 
>     "3" pt _ Point x: 25 y: 125.
> 
> would have had the same effect as step "2".
> 
> There is actually a problem with using Point new.  We normally think of
> a Point as an object having some kind of number for an x coordinate and
> some kind of number for a y coordinate (and possibly other stuff it is
> belongs to a subclass of Point), but
>     "1" pt _ Point new
> returns a new point such that pt x is nil and pt y is nil.  Another way
> to come up with a suitable point would be
> 
>     "4" pt _ Point new x: 25; y: 125.
> or
>     "1'" pt _ Point new.
>     "2'" pt x: 25; y: 125.

Hi Richard thank for your reply. The point for me is now so clear
that I'm feeling stupid to didn't perceive it sooner. 25 at 125 create a
point, it is not only an assignation of values to x and y part of a
point.

Raymond