Show dynamic value as a number

[Swamp Thing]

TL;DR Summary

How to force expressions containing dynamic variables to display as numeric values?

In the example below, x is static while x1 is a dynamic copy of x. Also, y and z are similar expressions containing x and x1 respectively.
If we evaluate expressions containing x and x1, they display in numeric and mathematical formats, respectively (y and z below). How can I display z as a plain numeric value just as y is displayed?

 

[Dale]

That is weird. Why is y displayed like that? It should be displayed like z.

 

[Dale]

Something is wrong with your y. That value is not correct and it should not be displayed like that. However, I also cannot get it to display as a single decimal. The closest I get is

z = N[Sqrt[x1/2/Pi]]

But this gives $0.398942 \sqrt{200}$

 

[jedishrfu]

Is it because defining x1 as dynamic that symbolic evaluation is being done?

Have you tried the eval() function on your dynamic expression?

 

[Swamp Thing]

Something is wrong with your y.

Yes, there was. I corrected that, and now the y needs to be fed through N[] in order to see the numeric.

Have you tried the eval() function on your dynamic expression?

Neither N[] nor Evaluate[] are helpful in the dynamic case.

 

[jedishrfu]

Still looking but found an R Cookbook reference

https://rc2e.com/

 

[Swamp Thing]

This may explain the problem (but I'm still trying to understand it fully) :
https://reference.wolfram.com/language/tutorial/IntroductionToDynamic.html#1063215934

It seems to imply that you can't use Dynamic as an input to other functions, because it never goes to the kernel. It's just a directive for the front end.

The solution is probably to make sure that Dynamic encloses all the code that is going to use the variable that we want to make dynamic. I am experimenting along these lines.

But if we put Dynamic around a whole block of code, and if that block of code references many global variables, then it has no way to know which ones we want it to watch and respond to. All global variables would become dynamic. There must be a way to make it dynamic with respect to some selected variables and ignore changes in others?