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How to write ‘object oriented’ code

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  How to write ‘object oriented’ code Cecil Westerhof <Cecil@decebal.nl> - 2013-07-31 09:29 +0200
    Re: How to write ‘object oriented’ code luser- -droog <mijoryx@yahoo.com> - 2013-07-31 00:56 -0700
      Re: How to write ‘object oriented’ code luser- -droog <mijoryx@yahoo.com> - 2013-07-31 01:25 -0700
        Re: How to write ‘object oriented’ code luser- -droog <mijoryx@yahoo.com> - 2013-07-31 01:28 -0700
        Re: How to write ‘object oriented’ code luser- -droog <mijoryx@yahoo.com> - 2013-08-01 01:58 -0700

#1532 — How to write ‘object oriented’ code

I am using postscript to generate quotes with borders. For example at:
    https://www.facebook.com/CecilWesterhof

There are severall functions you need:
- drawing the actual border
- getting the height of the border
- getting the width of the left element
- getting the width of the right element
- getting the width of the center elements

Is there a (best) way that I can work like I am having classes? I just
make an assignment of the type of the border I want to use, and the
calls give the values belonging to that border.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#1533

On Wednesday, July 31, 2013 2:29:37 AM UTC-5, Cecil Westerhof wrote:
> I am using postscript to generate quotes with borders. For example at:
> 
>     https://www.facebook.com/CecilWesterhof
> 
> There are severall functions you need:
> 
> - drawing the actual border
> - getting the height of the border
> - getting the width of the left element
> - getting the width of the right element
> - getting the width of the center elements
> 
> 
> Is there a (best) way that I can work like I am having classes? I just
> make an assignment of the type of the border I want to use, and the
> calls give the values belonging to that border.
> 

For the simpler uses of Object-orientation
(abstraction, encapsulation), you can use dictionaries
for classes and objects.

Here's a very simple example of an encapsulated turtle:

http://stackoverflow.com/a/8624246/733077

And for serious OO in PS, this is the only Prior Work I've
found, but the code needs modification since it uses non-standard operators:

http://code.google.com/p/xpost/downloads/detail?name=monterey86.pdf

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#1534

On Wednesday, July 31, 2013 2:56:39 AM UTC-5, luser- -droog wrote:
> On Wednesday, July 31, 2013 2:29:37 AM UTC-5, Cecil Westerhof wrote:
> 
> > I am using postscript to generate quotes with borders. For example at:
> 
> >     https://www.facebook.com/CecilWesterhof
> > There are severall functions you need:
> 
> > - drawing the actual border
> > - getting the height of the border
> > - getting the width of the left element
> > - getting the width of the right element
> > - getting the width of the center elements
> > 
> > Is there a (best) way that I can work like I am having classes? I just
> > make an assignment of the type of the border I want to use, and the
> > calls give the values belonging to that border.
> 
> For the simpler uses of Object-orientation
> (abstraction, encapsulation), you can use dictionaries
> for classes and objects.
> 
> Here's a very simple example of an encapsulated turtle:
> 
> http://stackoverflow.com/a/8624246/733077
> 
> And for serious OO in PS, this is the only Prior Work I've
> 
> found, but the code needs modification since it uses non-standard operators:
> 
> http://code.google.com/p/xpost/downloads/detail?name=monterey86.pdf

For data-hiding, remember you can set access permissions
on a per-object basis, except for dictionaries.
So you can't do this:

/obj <<
    /data9 null
    /data1 null
>> def
obj begin
    /method0 { //obj /data0 get ... } def
    /method1 { //obj /data1 37 put ... } def
end
/obj obj readonly def

Because the readonly applies to the shared dictionary
as a whole. So you'd have to stuff your data into an
array, where you can have multiple handles with different
access. Something more like this:

/obj <<
    /private [
        <<
            /data0 null
            /data1 null
        >>
    ]
>> def
obj begin
    /method0 {//private 0 get /data0 get ... } def
    /method1 {//private 0 get /data1 37 put ... } def
end
obj /private 2 copy get readonly put

Now 
    obj /private get
will throw an error. But the methods grabbed the
array object before the access was changed (first
in the array object on the stack, and then in the
array object keyed /private in the obj dict),
and so the array objects embedded in the procedures
still have full access.

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#1535

On Wednesday, July 31, 2013 3:25:18 AM UTC-5, luser- -droog wrote:

> 
> Because the readonly applies to the shared dictionary
> as a whole. So you'd have to stuff your data into an
> array, where you can have multiple handles with different
> access. Something more like this:
> 
> /obj <<
>     /private [
>         <<
>             /data0 null
>             /data1 null
>         >>
>     ]
> >> def
> 
> obj begin
>     /method0 {//private 0 get /data0 get ... } def
>     /method1 {//private 0 get /data1 37 put ... } def
> end
> 
> obj /private 2 copy get readonly put
> 
> Now 
>     obj /private get

      0 get % <-- using the array, that is!

> will throw an error. But the methods grabbed the
> array object before the access was changed (first
> in the array object on the stack, and then in the
> array object keyed /private in the obj dict),
> and so the array objects embedded in the procedures
> still have full access.

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#1547

On Wednesday, July 31, 2013 3:25:18 AM UTC-5, luser- -droog wrote:
> On Wednesday, July 31, 2013 2:56:39 AM UTC-5, luser- -droog wrote:
> 
> > On Wednesday, July 31, 2013 2:29:37 AM UTC-5, Cecil Westerhof wrote:
> 
> > > I am using postscript to generate quotes with borders. For example at:
> 
> > >     https://www.facebook.com/CecilWesterhof
> 
> > > There are severall functions you need:
> > 
> > > - drawing the actual border
> > > - getting the height of the border
> > > - getting the width of the left element
> > > - getting the width of the right element
> > > - getting the width of the center elements
> > > 
> > > Is there a (best) way that I can work like I am having classes? I just
> > > make an assignment of the type of the border I want to use, and the
> > > calls give the values belonging to that border.
> 
> > For the simpler uses of Object-orientation
> > (abstraction, encapsulation), you can use dictionaries
> > for classes and objects.
> > 
> > Here's a very simple example of an encapsulated turtle:
> > 
> > http://stackoverflow.com/a/8624246/733077
> > 
> > And for serious OO in PS, this is the only Prior Work I've
> > 
> > found, but the code needs modification since it uses non-standard operators:
> > 
> > http://code.google.com/p/xpost/downloads/detail?name=monterey86.pdf
> 

[Revised version of previous post.]
 
 
 For data-hiding, remember you can set access permissions
 
 on a per-object basis, except for dictionaries.
 
 So you can't do this:
 
 
 
 /obj <<
     /private <<
         /data9 null
         /data1 null
     >>
 >> def
 obj begin
     /method0 { //obj /data0 get ... } def
     /method1 { //obj /data1 37 put ... } def
 end
 obj /private 2 copy get readonly put
 
 Because the readonly applies to the shared dictionary
 as a whole. So you'd have to stuff your data into an
 array, where you can have multiple handles with different
 access. Something more like this:

 /obj <<
 
     /private [
 
         <<
 
             /data0 null
 
             /data1 null
 
         >>
 
     ]
 
 >> def
 
 obj begin
 
     /method0 {//private 0 get /data0 get ... } def
 
     /method1 {//private 0 get /data1 37 put ... } def
 
 end
 
 obj /private 2 copy get readonly put
 
 
 
 Now 
 
     obj /private get
     0 get 
 
 will throw an error. But the methods grabbed the
 
 array object before the access was changed (first
> 
> in the array object on the stack, and then in the
> 
> array object keyed /private in the obj dict),
> 
> and so the array objects embedded in the procedures
> 
> still have full access.

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