My 2 cents:

According to a recent 4D blog entry, using the new object notation option
will speed up your objects significantly:

"Good news, now you have a mean to get rid of all those OB Get
<http://doc.4d.com/4Dv16R4/4D/16-R4/OB-Get.301-3318080.en.html> and OB SET
<http://doc.4d.com/4Dv16R4/4D/16-R4/OB-SET.301-3318074.en.html> in your
code! And you know what? The code execution is *10 times faster with the
object notation* compared to OB Get
<http://doc.4d.com/4Dv16R4/4D/16-R4/OB-Get.301-3318080.en.html>/OB SET
<http://doc.4d.com/4Dv16R4/4D/16-R4/OB-SET.301-3318074.en.html> usage!"

See http://blog.4d.com/another-way-of-coding-object-notation/?

You'll need to be using v16r4 I believe. But even if you're not on v16 yet,
it's worth keeping in mind.

Pat

On 21 July 2017 at 09:22, Nigel Greenlee via 4D_Tech <4d_tech@lists.4d.com>
wrote:

> Global Variables.
>
> Regardless of the relative merits of Arrays vs Object. I would like to
> relay my dislike in general of Global variables. I have been working with
> 4D since before the concept existed-since 4D V2(Globals came in with V3).
> Yes i am one of the old boys.
>
> Back then we did not have multiple processes and when V3 arrived we were
> all amazed and in awe of the ability to have multiple processes and I think
> we all went mad for interprocess(global) variables.(i think we all had
> singing dancing palettes on the screen doing fancy things to update
> themselves from other processes).
>
> Now if we were working in Javascript the concept of a global variable
> would very much be considered something to be avoided like the plague.
> Global variables are extremely useful but also extremely prone to problems,
> and over the past couple of years-any javascript tutorial tells you to try
> and avoid them, in 4D  I  have really cut down on my use of them.
>
> In my opinion a global variable should in general only be used for two
> things.
> 1) You want to set a value(or group of values) and through the life of the
> programme they do not change once set(so here you are using them like a
> constant)
> 2) You want to maintain an array that will be written to by multiple
> processes.
>
> With point 2 you must protect the arrays with semaphores so only one
> process alters the arrays at any one time-and often where these are used
> there might be other ways to do it.
>
> I have just this week been dealing with 2 different structures where the
> liberal use of interprocess arrays has lead to problems. Problems that do
> not show up in testing and probably show that that the way the routines has
> been used has changed over time. In both cases-different
> companies-different programmers-different stuff an error shows up just
> occasionally. In one of those systems discussion with the client shows that
> the usage of interprocess variables has caused ‘strange’ unexplained
> un-investigated things to happen where process A is changing the contents
> of <>Variable just at the point when process B is about to send the
> contents of <>Variable that process B had set to a document (‘sometimes we
> get a situation where the same order document is created twice’!!)..and
> they have just restarted the machine to get rid of the problem in the
> past(a practice that means you think the problem is 4D not the way the code
> is written).
>
> Simply protecting the handling so only one process at a time can modify
> the interprocess variables and arrays would have avoided all this. I
> suspect the original programmer never intended the functionality to be
> running in multiple processes at the same time and used interprocess arrays
> to (I think) make it easier to display the data on a form that is in a
> different process. Beyond the idea of a form in a different process i don’t
> see any purpose in the arrays in this case being interprocess-they are
> being constantly changed and as such should at best have been process
> arrays, In fact in a modern context(this was written way before that) where
> we have been able to pass pointers to local variables since 4D V11(??-maybe
> it was before that) I would generally argue that programming using locals
> is much better-and that could be local objects or local arrays. These
> really show that an interprocess array was used for convenience where it
> was not really needed and changes to code did not include a proper
> assessment of the impact-just because you can do something and it works
> once does not mean it is tested or fit for purpose.
>
> In most of my code over the past few years I have moved so far away from
> <> variables that if i have more than a few-maybe a variable holding the
> user name or something like that which does not change(and even there I use
> a function ..UTIL_GetUser(“Name”)..). I have even moved largely away from
> process variables and arguable could move further from them by not using
> variable names on screen objects. Convincing clients to let me change their
> code and actually changing it is not easy-in one case about the changes to
> the code are on a live system running uncompiled and this morning i am
> going to be attempting to apply a knife to this code.
>
>
> Most code i write now is ‘self contained’ -I attempt to set all values
> used in the method is passed in to the code -either as parameters or an
> object or a pointer to something so that i end up with something more like
> a javascript function. Myreturn:=MyMethod(something;something;something).
> Using this style of coding means i am far more likely to get an error if
> there is one EVERY TIME rather than a head scratching randomly appearing
> one and my code does not rely on the perceived value of a variable.
>
> Consider
>
> If(<>SOmething=1)
> //do something
> end if
>
> as soon as you have more than process where <>something is set you run the
> risk that at some point process A will set <>something to 1 and before it
> tests if <>something =1 process b changes <>something to 0 so you put a
> semaphore to stutter your code..
>
> if you write
>
> if(something=1)
> //do something
> end if
>
> //now process B can do whatever it likes with something and process A will
> not be affected but you still run the risk that somewhere you call this
> function before you have C_Longint(something) and something is not
> initialised. Even if ‘something’ should be initialised to the value of
> '<>something' this should be done at the start of the process and never use
> '<>something’ in the code. When i find code that uses '<>something' or
> ‘something'i have to look to see where something is set what changes it and
> work out everything about it.
>
> if you write
> C_LONGINT($something)
> if(Count parameters>=1)
> $something:=$1
> end if
>
> if($something=1)
> //do something
> end if
>
> You have code that is not dependent on the value of a variable it is only
> dependent on a value being passed in, and that might mean that the calling
> method also can use a local. This means i only need to see where my code is
> called and check that it is passing a relevent value to the code-much
> easier to track down a fault.
>
> This is a simple ‘one step’ example but I frequently see code chains like
> this.
>
> Methoda sets var-calls-method b-calls-method c-calls method d-and method d
> has if(var set in method a), and that is really where this chain of
> handling becomes a mess-we have method and the variable is set 3/4 levels
> up or worse set at startup in the code.
>
> If you pass an object the concept can become of course much more flexible,
> and slowly i am trying to adopt an object passing approach
>
> C_OBJECT($Something)
> If(Count parameters>=1)
> $Something:=$1
> end if
>
> if($Something.setting=1)
> //do something
> end if
>
> Becomes much easier to read(no unpacking the object here).
>
> After all its used extensively in javascript where passing json normal and
> with V16 now using dotted notation for getting at object item is a big
> encourement to utilize this(yet to test that out myself).
>
>
>
> Are other people taking this approach to the use of variables. How easy
> are you finding it retro-fitting it to existing code?
>
>
> Nigel Greenleee
>
>
>
>
>
> > On 18 Jul 2017, at 16:29, Chip Scheide via 4D_Tech <4d_tech@lists.4d.com>
> wrote:
> >
> > Long ago - and I am pretty sure the code has been lost to time -
> > in v2.2.3 (I think) I wrote code to do binary searching on a selection,
> > as at that time Search Selection (the old command name) was sequential,
> > but sorting the selection was indexed.
> >
> > Even with the overhead of managing the pointers, and stepping through
> > records to find all matching records in the selection, as memory
> > serves, it was faster (interpretedly) to use the binary search on a
> > selection size of beginning at 6-8 records.
> >
> > For those who care, an outline of a binary search (on records in
> > selection)
> > The following was written off the stop of my head, in the email editor,
> > BUT it gets to the basics of a binary search on a selection in 4D.
> >
> > - get size of selection ($Selection_Size).
> > - make sure it is sorted on the field you want to search on.
> >
> > repeat
> > $Current_record:= int($Selection_Size/2)
> >
> >   repeat
> >    goto selected record([table];$Current_record)
> >     case of
> >      :($Current_record>=$Selection_Size) or ($Current_record<=1)
> >      $Not_Found:=true
> >      :([table]field = Value)  // found it create collection of
> > matching records
> >       add to set([table];"Matching")
> >       $previous:=$Current_record
> >       $Next:=$Current_record
> >
> >        repeat
> >          $previous:= previous-1
> >          goto selected record([table];$previous)
> >
> >          if ([table]field = Value)  // found it create collection of
> > matching records
> >            add to set([table];"Matching")
> >          else
> >            $previous:=0
> >          end if
> >        until($previous=0)
> >
> >        repeat
> >          $$Next:= $Next+1
> >          goto selected record([table];$Next)
> >
> >          if ([table]field = Value)  // found it create collection of
> > matching records
> >            add to set([table];"Matching")
> >          else
> >            $Next:=Selection_Size
> >          end if
> >        until($Next= Selection_Size)
> >        $Mo_More_Matches = true
> >      :([table]field > Value)  // Not found current record value >
> > search value
> >       $Current_record:=int((1+$Current_record)/2)
> >      :([table]field < Value)  // Not found current record value <
> > search value
> >       $Current_record:=int((Selection_Size+1+$Current_record)/2)
> >      end case
> > until ($Not_Found)) or ($No_More_Mathes)
> >
> > At this point the set "Matching" contains all records matching the
> > criteria, or nothing.
> >
> > On Tue, 18 Jul 2017 22:16:18 +1000, David Adams via 4D_Tech wrote:
> >>
> >> And, lest anyone forget, you can use binary search logic on sorted
> >> selections with GOTO SELECTED RECORD. Why not?
> > ---------------
> > Gas is for washing parts
> > Alcohol is for drinkin'
> > Nitromethane is for racing
> > **********************************************************************
> > 4D Internet Users Group (4D iNUG)
> > FAQ:  http://lists.4d.com/faqnug.html
> > Archive:  http://lists.4d.com/archives.html
> > Options: http://lists.4d.com/mailman/options/4d_tech
> > Unsub:  mailto:4d_tech-unsubscr...@lists.4d.com
> > **********************************************************************
>
> **********************************************************************
> 4D Internet Users Group (4D iNUG)
> FAQ:  http://lists.4d.com/faqnug.html
> Archive:  http://lists.4d.com/archives.html
> Options: http://lists.4d.com/mailman/options/4d_tech
> Unsub:  mailto:4d_tech-unsubscr...@lists.4d.com
> **********************************************************************
>



-- 
*************************************************
CatBase - Top Dog in Data Publishing
tel: +44 (0) 207 118 7889
w: http://www.catbase.com
skype: pat.bensky
*************************************************
**********************************************************************
4D Internet Users Group (4D iNUG)
FAQ:  http://lists.4d.com/faqnug.html
Archive:  http://lists.4d.com/archives.html
Options: http://lists.4d.com/mailman/options/4d_tech
Unsub:  mailto:4d_tech-unsubscr...@lists.4d.com
**********************************************************************

Reply via email to