Nesting DynamicVariables

I have a list of DyamicVariables that I would like to set at the same time.

If there were two in the list the code would look like so.

state: state during: aBlock

DynamicVar1
    use: (DynamicVar newValueFor: state)
    during: [  DynamicVar2
                      use: (DynamicVar newValueFor: state)
                      during: aBlock                                  
      ]
 

Now if there were any number of this things in an OrderedCollection how
would I efficiently or otherwise evaluate this code nested n times deep.

thanks in advance

Keith

> Now if there were any number of this things in an OrderedCollection how
> would I efficiently or otherwise evaluate this code nested n times deep.

The easiest would be if you let a specific dynamic variable return an
object (e.g. an ordered-collection or a dictionary), that knows all
your objects.

There is also the package DynamicBindings, that provides a whole
framework for doing things like this.

Lukas

--
Lukas Renggli
http://www.lukas-renggli.ch

Lukas Renggli wrote:
Hi Lukas,

Overnight I came to the same conclusion, that what I was trying was too
complex for a simple problem.

I am trying to support a number of orthogonal requirements on WASession
without subclassing, but it doesnt have a properties dictionary where I
can stuff things. I need slots for more than one db session, and an
announcements announcer amongst other things.

Thanks for the suggestion, I could have just one other DynamicVariable
working in tandem with WACurrentSession and that could hold the other
values.

How performant are these DynamicVariable lookups?

many thanks

Keith

> How performant are these DynamicVariable lookups?

They are quite performant, if your stack has a reasonable size and you
are calling the lookup a reasonable number of times. There is a
primitive in the VM that answers the next context possible handler.

I remember a project where dynamic variables were used to translate
every individual string displayed on the page. The rendering was not
measurably slower than in the untranslated case.

If you need raw speed, it might be smart to add an additional variable
to Process which provides you with O(1) performance. However since
this is much trickier to port, we don't use it in Seaside.

I am co-author of an not yet published paper that compares the two
approaches in the discussion. The observed numbers for 10^6 queries
are the following:

        Stack depth Dynamic Variables Process Variable
        0 7455 ms 258 ms
        100 7967 ms 258 ms
        1000 17883 ms 255 ms

Cheers,
Lukas

--
Lukas Renggli
http://www.lukas-renggli.ch