Re: Slider and Dynamic implementation details
- To: mathgroup at smc.vnet.net
- Subject: [mg83978] Re: Slider and Dynamic implementation details
- From: dh <dh at metrohm.ch>
- Date: Thu, 6 Dec 2007 02:39:02 -0500 (EST)
- References: <email@example.com>
see below, Daniel
Otto Murphy wrote:
> Hey all,
> I'm curious about the workings of Mathematica 6's dynamic functionality.
> Specifically the interaction between Slider and Dynamic in this simple
> Slider[Dynamic[x, (x = 1 - #) &]]
> Okay so my first question involves removing the first embedded dynamic and
> leaving just the x, like so:
from the manual: Slider[Dynamic[x]] will reset the value of x when the
slider is moved; Slider[x] will not.
> Intuitively, to me, the slider function should still be able to update the
> value of x and the dynamic should still be able to display those updated
> values. Like if slider were just like a normal function that updates the
> value of x in the kernel just like a new assignment statement would. BUT,
> this doesn't happen--X doesn't change. This makes me think there's some
> special mechanism here. Could someone explain it?
> My second question has to do with the second argument to Dynamic. Again,
> intuitively, to me, it seems like when dynamic looks for an updated value of
> x, it uses that function to assign it it's new value. But this couldn't be
> completely true because it doesn't work like this:
> Dynamic[Dynamic[x, (x = 1 - #) &]]
> The dynamic display of x doesn't seem to use the function--it only works
> when it's in slider. Why is that?
First, I do not see any reason for a double "Dynamic". Second, how do
you decide that: "The dynamic display of x doesn't seem to use the
function". E.g. you can not simply say: Dynamic[x, (x = 1 - #) &], this
would make a definition for Dynamic not x. To assign to x, you simply
need to write x=...
> I looked through the documentation and didn't see anything addressing these
> kinda picky questions, but I'm just darn curious. Although Mathematica isn't
> open source, I'm assuming there are plenty of people out there who are
> familiar with implementation details like these.
> Thanks a lot for the help!
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