So I am not terribly sure why creating a closure should should mess with the scoping of the variables. I'm not sure this is the desired behaviour. Maybe there is a good reason. Clearly in this scenario, the compiler is confused by what "z" is.
Its just that printing a variable without implicitly or explicitly declaring it first in a lexical scope seemed like a code smell to me. That was the first thought on debugging this. Regards - Avik On Wednesday, 29 April 2015 05:57:09 UTC+1, Pooya wrote: > > Ah! Thank you. I had not heard of closure before. Now, I have heard of it, > but am not sure if I can completely understand it! I guess this might be > worth being explained in the manual. One thing that is still kind of > confusing is that in your example, z is defined after the closure is > created until the end of that iteration. So, z is printed once below, but > not the second time in the beginning of the second iteration! > > julia> for i=1:10 > if i>=2; println(z); end > z=2 > g()=2z > println(z) > end > 2 > ERROR: z not defined > in anonymous at no file:2 > > > On Tuesday, April 28, 2015 at 10:17:17 PM UTC-4, Avik Sengupta wrote: > >> Yes, sorry I jumped the gun. Thanks for clarifying. >> >> But it still does not have anything to do with Optim :) >> >> The problem is due to defining an inline function (line 43) that creates >> closure over the "x_previous" variable. To test this, just comment that >> line (and adjust the Optim.optimize call), the problem goes away. >> >> A simpler version of the code that fails is as follows: >> >> julia> function f() >> for i=1:10 >> if i>2; println(z); end >> z=2 >> g() = 2z >> end >> end >> f (generic function with 1 method) >> >> julia> f() >> ERROR: z not defined >> in f at none:3 >> >> A fix to get it to work is to declare the variable at the start of your >> function. Similarly, adding a "local x_previous" at the top of your >> function makes it work correctly. Remember, variables in Julia are lexical >> in scope. >> >> julia> function f() >> local z >> for i=1:10 >> if i>2; println(z); end >> z=2 >> g()=2z >> end >> end >> f (generic function with 1 method) >> >> julia> f() >> 2 >> 2 >> 2 >> 2 >> 2 >> 2 >> 2 >> 2 >> >> >> On Wednesday, 29 April 2015 02:23:28 UTC+1, Pooya wrote: >>> >>> If you comment out lines 42-49, you will see that it works fine! >>> >>> On Tuesday, April 28, 2015 at 9:20:49 PM UTC-4, Pooya wrote: >>>> >>>> Thanks, but I think "if iter > 2" (line 21) makes sure that x_previous >>>> is defined in the previous iteration. Just to be clear, the condition to >>>> check here was "g_norm > g_norm_old", but I changed it to get there as >>>> early as the second iteration. >>>> >>>> On Tuesday, April 28, 2015 at 9:13:49 PM UTC-4, Avik Sengupta wrote: >>>>> >>>>> I'm seeing the error in line 22 of your gist where you are trying to >>>>> print the current value of "x_previous". However, x_previous is first >>>>> defined in line 38 of your gist, and so the error is correct and doesnt >>>>> have anything to do with Optim, as far as I can see. >>>>> >>>>> On Wednesday, 29 April 2015 01:39:02 UTC+1, Pooya wrote: >>>>>> >>>>>> Hi all, >>>>>> >>>>>> I have a problem that has made me scratch my head for many hours now! >>>>>> It might be something obvious that I am missing. I have a Newton-Raphson >>>>>> code to solve a system of nonlinear equations. The error that I get here >>>>>> does not have anything to do with the algorithm, but just to be clear, I >>>>>> need to find the best possible solution if the equations are not >>>>>> solvable, >>>>>> so I am trying to stop simulation when the direction found by >>>>>> Newton-Raphson is not correct! In order to do that I put an if-loop in >>>>>> the >>>>>> beginning of the main loop to take x from the previous iteration >>>>>> (x_previous), but I get x_previous not defined! I am using the Optim >>>>>> package to do a line search after the direction has been found by >>>>>> Newton-Raphson. If Optim is not used, things work perfectly (I tried by >>>>>> commenting out those lines of code). Otherwise I get the error I >>>>>> mentioned. >>>>>> My code is here: >>>>>> https://gist.github.com/prezaei85/372bde76012472865a94, which solves >>>>>> a simple one-variable quadratic equation. Any thoughts are very much >>>>>> appreciated. >>>>>> >>>>>> Thanks, >>>>>> Pooya >>>>>> >>>>>
