## If No PayPal or CreditCard, What other alternatives solution for making international payments ?

I know this must have been asked several times already but what is the definitive solution without having any issues ?

My cc already got deactivated twice because some international sellers have not implemented 3d secure verification. Same problem with PayPal. Even if the transaction goes through the cc issuer calls to get confirmation and if I am not reachable on the phone they deactivate my card.

The cc company also blocked a verification amount charged by Entropay and warned me not to…

If No PayPal or CreditCard, What other alternatives solution for making international payments ?

## Solution for a large amount of user logins [closed]

I’m looking to build a site for a friend but it has to support user logins (with custom roles) in the thousands and this is where I’m stuck.

I’m looking to make it a static site hosted on netlify and netlify has an identity service that lets you have 1000 user accounts with roles in the free version and a bit more but at a big price jump of \$ 99/month.

I also looked at auth0 because it offers 7k user accounts for the free tier but no custom roles and in order to get custom roles you need to upgrade to the next tier which actually cuts down the amount of accounts you can have to 1k.

I’m not sure how else to handle this many user accounts without a hefty price. I could maybe host a database on a cheap server but I feel like costs might get out of control with that as well.

## Canonical solution of a scoping problem

Scoping is a recurrent issue on this forum.

Yet, I stumble again and again at the same thing. Googling over this site does not quickly bring a solution. Two reasons:

1. There are many low quality answers such as this one (and I can elaborate on this, if needed).
2. There are many very good answers (this and this), but they are too long.

Sometimes I just want to learn by examples, not by reading many pages of dry theory. Therefore I would like to ask this question again even at risk being downvoted or the question being closed.

Consider this code

ClearAll[g,i,list];  list=Range[3] g[l_]:=Module[{i},l/.{i_->2i}]  g[list] i=5 g[list]  Out[2]= {1,2,3} Out[4]= {2,4,6} Out[5]= 5 Out[6]= 10 

Or a very similar one

ClearAll[g,i,list];  list=Range[3] g[l_]:=Cases[l,i_->2i]  g[list] i=5 g[list]  Out[8]= {1,2,3} Out[10]= {2,4,6} Out[11]= 5 Out[12]= {10,10,10} 

It is clear to me that setting the global variable i interferes with the function definition. I would like to know what is the canonical way of avoiding this interference?.

Please, avoid answer like 2 list.

## How to obtain eigenvalues from an ODE’s general solution?

For this second-order linear ODE (eigenvalue e) $$y”(x) – 2g\, y'(x) + [-e + g^2 – (\frac{b^2x^2}{2}+a)^2 + b^2x]\, y(x)=0$$ I know the correct analytical general solution form with two undetermined constants c1,c2 (verified in the code below where y1,y2 is given) $$y=c1\,y1(x)+c2\,y2(x)$$ I want to impose the boundary condition $$y(\pm5)=0$$ in order to get the eigenvalue $$\lambda$$. (Actually $$y(\pm\infty)=0$$, but not much numerical difference, I suppose.) So I put c1=1 and tried FindRoot e and c2 together, but it didn’t work well. So I was wondering if I need to tune any option or some other methods?
I also add a direct numerical solution as a reference.

F := (D[#, {x, 2}] -       2 g D[#, x] + (-e + g^2 - (b^2 x^2/2 + a)^2 + b^2 x) #) &; y1[x_] := E^(-(1/6) b^2 x^3 - x a + x g) HeunT[e, 0, -2 a, 0, -b^2, x]; y2[x_] := E^(-(1/6) b^2 x^3 - x a + x g) HeunT[e, 0, -2 a, 0, -b^2, x]; y[x_] := c1 y1[x] + c2 y2[x]; F[y[x]] == 0 // FullSimplify  g = 0.2; a = 0.3 - I 0.3; b = 1; FindRoot[0 ==     y[x] /. {{c1 -> 1, x -> 5}, {c1 -> 1, x -> -5}}, {{e, -0.3}, {c2,     1}}, WorkingPrecision -> 55]  FF = F /. e -> 0; {vals, funs} = NDEigensystem[FF[yy[x]], yy[x], {x, -5, 5}, 5]; vals Plot[Evaluate@Abs@funs, {x, -5, 5}, PlotRange -> All,   PlotLegends -> Automatic] 

## Steady state solution (1D) of nonlinear dispersal equation

Now I’m interested in the equation $$\frac{\partial }{\partial x}\Bigl(\text{sgn}(x) u \Big) +\frac{\partial}{\partial x} \Bigl[ u^2 \frac{\partial u}{\partial x} \Bigr] =0$$ with boundary conditions $$u(-5)=u(5)=0$$

Since $$\text{sgn}(x)$$ is not differentiable at $$x=0$$, I expectd ND solve to have some problems. I tried

sol = NDSolveValue[{   0 == D[Sign[x]*u[x],x] + D[u[x]^2 D[u[x], x], x],    u[-6] == 0, u[6] == 0}   , u, {x, -7, 7}] 

but I can’t even plot it and I think that I’m writing it in the wrong way. Could someone confirm I wrote the right snippet and show the plot I should obtain?

• I asked a related question three days ago, where the equation was the PDE $$\partial_t u = \partial_x (\text{sign}(x) u) + \partial_x (u^2\partial_x u)$$. The one I have above it’s the steady state solution, and I want to compute it directly, instead of integrating in time.

## Email Contact forms problems. Need an affordable solution. Suggestions?

I am having issues with my email contact forms not working. I need to find someone or a company who can help me establish web contact forms for my sites that work and will continue working.

## Is My Recurrence Solution Correct? (Substitution method)

nvmnvmnvmnvmnvmnvmnvmnvmnvmnvmnvmnvmnvmnvm

## Offline bin-packaging problem: probability of a non-optimal solution for the first-fit-decreasing algorithm

For the offline bin packaging problem (non-bounded number of bins, where each bin has a fixed size, and a input with known size that can be sorted beforehand), the first-fit-decreasing algorithm (FFD) gives a solution whose number of bins is, at most, $$\frac{11}{9}\times S_{opt} + \frac{6}{9}$$, or, for the sake of simplification, around $$23\%$$ bigger than the optimal number of bins ($$S_{opt}$$).

Has the probability of getting a non-optimal solution using FFD been ever calculated? Or, in other words, what is the probability of getting a solution whose exact size is $$S_{opt}$$? Or do we have no other choice than assuming that the solution size is evenly distributed in the interval $$[S_{opt}, \frac{11}{9}\times S_{opt} + \frac{6}{9}]$$? Or, as another alternative I can think of right now, is the solution size so dependant on the input that making this question has no sense at all?

And, as a related question, is there any research about what is the NP-hard or NP-complete problem that has an approximation algorithm (of polynomial asymptotic order) with the highest probability of providing an optimal solution?

## What should players roll to “deduce” a solution?

Say my players are in a dungeon of many keys and many doors, where if a wrong key is used in the wrong door, they will be electrocuted, ambushed, etc. This makes the players wary to just try every key in every door. The players have found a key that I describe as "a simple key, made of copper stained green with age." Our session ends, and next week the players find a locked door. A perception check has them see the lock as "relatively simple, made of aged copper, turning green." Due to my players lack of note taking and poor memory over a week, they do not associate the key with the lock. In this scenario the players may have forgotten, but the characters likely wouldn’t have, but I do not want to just hand the players the answer.

After a few minutes of them unsuccessfully trying to get through the door that was never intended to be difficult puzzle, I want them to roll to recognize the similarities between the lock and the key they previously found.
An investigation check doesn’t seem appropriate, as they are not investigating anything for this, just thinking about it. A perception check doesn’t seem fitting either, as they have already seen the lock and key, they just need to recognize the similarities between them.

How should I have my players roll to deduce an answer to a simple question?

## File analysis solution

I scrolled through SA and didn’t find a better site. If there’s a better place to ask please let me know.

We’re in need of a file analysis solution. We need a way to analyze and assess files with unknown contents that in some cases may have confidential information within them. Due to this risk of confidential information we either need a reputable cloud based company with a strong privacy policy and security measures, or an on-prem solution, with on-prem being preferred.

Anyone here have any suggestions? We’re open to either static-analysis or dynamic-analysis in our situation.