[squeak-dev] Understanding Object Structures

Trygve Reenskaug trygver at ifi.uio.no
Sat Jan 17 11:06:23 UTC 2015

I suggest using BabySRI to help students internalize the difference 
between a class oriented and an object oriented mindset.  My message "A 
puzzle for the  New Year" of 02.01.2015 12:01 has an example.

On 16.01.2015 16:55, Eliot Miranda wrote:
> Hi All,
> On Jan 16, 2015, at 7:36 AM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> +++
> This is interesting.  (Marcel, Chris, forgive me; I'm presuming; please don't take this personally).  Marcel above appears to lack an intuition about the structure of Array vs LinkedList.  And in developing a hash algorithm for a 32-bit subset of Floats a few weeks ago Chris appeared to lack an I tuition about Floats being boxed, assuming they were value types, not containers.
> As a VM implementer I carry around a clear picture (literally, I am a visual thinker) of objects in my head.  Those pictures are key to my approach to design and optimization.
> I presume that for someone approaching the system given only a textual description of object structures, through class comments and method source it is difficult to develop a good picture or mental model.  For me, I read the blue book first, which is replete with pictures.
> I know that historically visual inspector frameworks such as Jun have been able to auto-generate pictorial representations of specific object graphs.  I wonder how useful it would be to provide support for designers to include pictorial representations in class comments.
> Again I presume that the text model would have to support inclusion of simple bitmaps (to avoid having to include a full drawing framework in the system) and that the designer would construct a sample graph, generate a diagram using a visual inspector framework using eg Jun, render it to a bitmap and include it in the class comment.
> A more elaborate system could of course include the sample graph and render it dynamically, that would allow exploration.
> Either approach would make an interesting project, yes?

The essence of object orientation is that
objects collaborate to achieve a goal.
The class hierarchy is in the nature of a comment;
it has no run time significance.
Trygve Reenskaug mailto: trygver at ifi.uio.no <mailto:%20trygver at ifi.uio.no>
Morgedalsvn. 5A http://folk.uio.no/trygver/
N-0378 Oslo http://fullOO.info
Norway                     Tel: (+47) 22 49 57 27

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