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• Generating unique N-valued key

  - by Bar

  Hi, StackOverflow! I want to generate unique random, N-valued key. This key can contain numbers and latin characters, i.e. A-Za-z0-9. The only solution I am thinking about is something like this (pseudocode): key = ""; smb = "ABC…abc…0123456789"; // allowed symbols for (i = 0; i < N; i++) { key += smb[rnd(0, smb.length() - 1)]; // select symbol at random position } Is there any better solution? What can you suggest? TIA, Michael.

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• Compact a given array problem

  - by Bragaadeesh

  Dont know whether this is a duplicate, but this was an interview question asked to me. Given an array of random numbers and -1 placed inbetween, I have to compact the array meaning all the -1s are to be replaced and the final output should be the last valid index with the fresh array. For example. Input: 3 4 -1 -1 -1 5 8 -1 8 Output: 3 4 5 8 8 5 8 -1 8 and last valid index is 4 Input: -1 -1 -1 -1 -1 2 Output: 2 -1 -1 -1 -1 2 and last valid index is 0 Input: -1 -1 -1 3 3 3 Output: 3 3 3 3 3 3 and last valid index is 2 You should not swap the values just the last valid index along with the array is enough to decipher the non negative values.

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• Sending a signup confirmation email with having to confirm using Devise

  - by slythic

  Hi all, I'm using devise to handle user authentication with my rails app. I'd like to allow my users to sign up and be instantly logged in and receive a confirmation email. Devise has the Confirmable module which sends out an email but requires the user to open up their mail application, find the email and click a link which then leads them to the site again. I'd like to just email the user a confirmation that they signed up and that's it. Is there a way for devise to do this or do I need to resolve to handling ActionMailer myself (if so, is there a quick and non-complex example)? Many thanks! -Tony

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• Needing to copy properties before validation

  - by Mikael

  I have a farily complex model needing to be validated, the problem is that this model is used on two different places, one where you register your customer and one where you simply add addresses. Some fields on the address are simply not visible on the register customer form. So when i check if ModelState.IsValid i get false of course since eg. the name is not entered on the billing address, but it is on the customer. That is why i want to before validation occurs, copy a couple of fields to the model, and then validate. I am somewhat lost though and i need help. My action looks something like this: public ActionResult Register(WebCustomer customer) { customer.CopyProperties(); if(TryUpdateModel(customer)) { ... } ... But it always returns false, and ModelState.IsValid continues to be false.

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• How to associate Wi-Fi beacon info with a virtual "location"?

  - by leander

  We have a piece of embedded hardware that will sense 802.11 beacons, and we're using this to make a map of currently visible bssid -> signalStrength. Given this map, we would like to make a determination: Is this likely to be a location I have been to before? If so, what is its ID? If not, I should remember this location: generate a new ID. Now what should I store (and how should I store it) to make future determinations easier? This is for an augmented-reality app/game. We will be using it to associate particular characters and events with "locations". The device does not have internet or cellular access, so using a geolocation service is out of consideration for the time being. (We don't really need to know where we are in reality, just be able to determine if we return there.) It isn't crucial that it be extremely accurate, but it would be nice if it was tolerant to signal strength changes or the occasional missing beacon. It should be usable in relatively low numbers of access points (e.g. rural house with one wireless router) or many (wandering around a dense metropolis). In the case of a city, it should change location every few minutes of walking (continuously-overlapping signals make this a bit more tricky in naive code). A reasonable number of false positives (match a location when we aren't actually there) is acceptable. The wrong character/event showing up just adds a bit of variety. False negatives (no location match) are a bit more troublesome: this will tend to add a better-matching new location to the saved locations, masking the old one. While we will have additional logic to ensure locations that the device hasn't seen in a while will "orphan" any associated characters or events (if e.g. you move to a different country), we'd prefer not to mask and eventually orphan locations you do visit regularly. Some technical complications: signalStrength is returned as 1-4; presumably it's related to dB, but we are not sure exactly how; in my experiments it tends to stick to either 1 or 4, but occasionally we see numbers in between. (Tech docs on the hardware are sparse.) The device completes a scan of one-quarter of the channel space every second; so it takes about 4-5 seconds to get a complete picture of what's around. The list isn't always complete. (We are making strides to fix this using some slight sampling period randomization, as recommended by the library docs. We're also investigating ways to increase the number of scans without killing our performance; the hardware/libs are poorly behaved when it comes to saturating the bus.) We have only kilobytes to store our history. We have a "working" impl now, but it is relatively naive, and flaky in the face of real-world Wi-Fi behavior. Rough pseudocode: // recordLocation() -- only store strength 4 locations m_savedLocations[g_nextId++] = filterForStrengthGE( m_currentAPs, 4 ); // determineLocation() bestPoints = -inf; foreach ( oldLoc in m_savedLocations ) { points = 0.0; foreach ( ap in m_currentAPs ) { if ( oldLoc.has( ap ) ) { switch ( ap.signalStrength ) { case 3: points += 1.0; break; case 4: points += 2.0; break; } } } points /= oldLoc.numAPs; if ( points > bestPoints ) { bestLoc = oldLoc; bestPoints = points; } } if ( bestLoc && bestPoints > 1.0 ) { if ( bestPoints >= (2.0 - epsilon) ) { // near-perfect match. // update location with any new high-strength APs that have appeared bestLoc.addAPs( filterForStrengthGE( m_currentAPs, 4 ) ); } return bestLoc; } else { return NO_MATCH; } We record a location currently only when we have NO_MATCH and the app determines it's time for a new event. (The "near-perfect match" code above would appear to make it harder to match in the future... It's mostly to keep new powerful APs from being associated with other locations, but you'd think we'd need something to counter this if e.g. an AP doesn't show up in the next 10 times I match a location.) I have a feeling that we're missing some things from set theory or graph theory that would assist in grouping/classification of this data, and perhaps providing a better "confidence level" on matches, and better robustness against missed beacons, signal strength changes, and the like. Also it would be useful to have a good method for mutating locations over time. Any useful resources out there for this sort of thing? Simple and/or robust approaches we're missing?

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• git: programmatically know by how much the branch is ahead/behind a remote branch

  - by Olivier

  I would like to extract the information that is printed after a github status, which looks like: # On branch master # Your branch is ahead of 'origin/master' by 2 commits. Of course I can parse the output of git status but this is not recommended since this human readable output is liable to change. There are two problems: How to know the remote tracked branch? It is often origin/branch but need not be. How to get the numbers? How to know whether it is ahead/behind? By how many commits? And what about the diverged branch case?

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• How to optimize MATLAB loops?

  - by striglia

  I have been working lately on a number of iterative algorithms in MATLAB, and been getting hit hard by MATLAB's performance (or lack thereof) when it comes to loops. I'm aware of the benefit of vectorizing code when possible, but are there any tools for optimization when you need the loop for your algorithm? I am aware of the MEX-file option to write small subroutines in C/C++, although given my algorithms, this can be a very painful option given the data structures required. I mainly use MATLAB for the simplicity and speed of prototyping, so a syntactically complex, statically typed language is not ideal for my situation. Are there any other suggestions? Even other languages (python?) which have relatively painless matrix tools are an option.

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• View a git diff-tree in a reasonable format

  - by Josh

  Howdy, I'm about to do a git svn dcommit to our svn repo -- and as is recommended in a number of places, I wanted to figure out exactly what I was going to be committing with a dry run. As such I ran: git svn dcommit -n This produced output: Committing to http://somerepo/svn/branches/somebranch diff-tree 1b937dacb302908602caedf1798171fb1b7afc81~1 1b937dacb302908602caedf1798171fb1b7afc81 How do I view this in a format that I can consume as a human? A list of modified files comes to mind. This is probably easy, but running git diff-tree on those hashes gives me a reference to a directory and a some other hashes, as well as some numbers. Not quite sure what to make of it. Thanks very much, Josh

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• Voting UI for showing like/dislike community comments side-by-side

  - by Justin Grant

  We want to add a comments/reviews feature to our website's plugin gallery, so users can vote up/down a particular plugin and leave an optional short comment about what they liked or didn't like about it. I'm looking for inspiration, ideally a good implementation elsewhere on the web which isn't annoying to end users, isn't impossibly complex to develop, and which enables users to see both good and bad comments side-by-side, like this: Like: 57 votes Dislike: 8 votes --------------------------------- -------------------------------- "great plugin, saved me hours..." "hard to install" "works well on MacOS and Ubuntu" "Broken on Windows Vista with UAC enabled" "integrates well with version 3.2" More... More... Anyone know a site which does something like this?

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• .net c# text box date with mask - setup

  - by flavour404

  I have a c# .net project and want an input text box for a date value. I want it to display a default value of mm/dd/yyyy and then allow users to enter valid dates. I have tried using a masked text box but it doesn't like having the above format. If i try and use //__ looks naff and so does 00/00/0000 and of course if you put in '0' like 03/11/2009 you get 3/11/29 because the 0's are deleted as part of the mask - so what is the best way to set up an input box like this, effectively with a mask, only allowing numbers, and validation (though at this point I am not so worried about that). This seems so simple and isn't. Thanks, R.

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• filter to reverse lines of a text file

  - by Greg Hewgill

  I'm writing a small shell script that needs to reverse the lines of a text file. Is there a standard filter command to do this sort of thing? My specific application is that I'm getting a list of Git commit identifiers, and I want to process them in reverse order: git log --pretty=oneline work...master | grep -v DEBUG: | cut -d' ' -f1 | reverse The best I've come up with is to implement reverse like this: ... | cat -b | sort -rn | cut -f2- This uses cat to number every line, then sort to sort them in descending numeric order (which ends up reversing the whole file), then cut to remove the unneeded line number. The above works for my application, but may fail in the general case because cat -b only numbers nonblank lines. Is there a better, more general way to do this?

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• Rails 3 nested forms with has_many :through, entry in join table dosen't get deleted after update

  - by Hadi S.

  Hi, i have a 'User' model which has a has_many relationship to a 'Number' model through a join table 'user_number' model. I use accepts_nested_attributes_for :numbers, :allow_destroy = true in the 'User' model. Everything works fine except that whenever i delete a number from a user in the edit form, the associated number is deleted correctly in the 'number' table, but not the entry in the 'user_number' join table. In the update controller action i only use this: ... if @user.update_attributes(params[:user]) ... How can i force rails to also delete the associated entry in the join table?

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• manipulating strings, search text

  - by alhambraeidos

  Hi all, I try explain my issue: note 1: I have only strings, not files, ONLY strings. I have a string like this (NOTE: I include line numbers for better explain) The line separator is \r\n (CRLF) string allText = 1 Lorem ipsum Lorem ipsum 2 == START 001partXXX.sql == 3 Lorem ipsum TEXT Lorem ipsum 4 == END 001partXXX.sql == 5 Lorem ipsum TEXT Lorem ipsum 6 == START 002partzzz.sql == 7 Lorem ipsum TEXT Lorem ipsum 8 == END 002partzzz.sql == I have contents strings like this: string contents1 = == START 001partXXX.sql == Lorem ipsum TEXT Lorem ipsum == END 001partXXX.sql == the other content string: string contents2 = == START 002partzzz.sql == Lorem ipsum TEXT Lorem ipsum == END 002partzzz.sql == Then, allText.IndexOf(contents1) != -1 allText.IndexOf(contents2) != -1 I need function thats receive 3 parameters: allText, Contents, and text to find in contents, and it returns the line number of Text To Find in AllText For example, input: allText, contents2, "TEXT" ouput = line number 7 Another sample, input: allText, contents1, "TEXT" ouput = line number 3 Another sample, input: allText, contents1, "TEXT NOT FOUND" ouput = line number -1 How can I implement this function ?? any help very useful for me, Thanks in advanced.

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• JavaScript distributed computing project

  - by Ben L.

  I made a website that does absolutely nothing, and I've proven to myself that people like to stay there - I've already logged 11+ hours worth of cumulative time on the page. My question is whether it would be possible (or practical) to use the website as a distributed computing site. My first impulse was to find out if there were any JavaScript distributed computing projects already active, so that I could put a piece of code on the page and be done. Unfortunately, all I could find was a big list of websites that thought it might be a cool idea. I'm thinking that I might want to start with something like integer factorization - in this case, RSA numbers. It would be easy for the server to check if an answer was correct (simply test for modulus equals zero), and also easy to implement. Is my idea feasible? Is there already a project out there that I can use?

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• Are all languages used within .net Equally performant?

  - by WeNeedAnswers

  I know the "Sales pitch" answer is yes to this question, but is it technically true. The Common Language Runtime (CLR) is designed as an intermediate language based on Imperative Programming (IP), but this has obvious implications when dealing with Declarative Programming (DP). So how efficient is a language based on a different paradigm than the Imperative Style when implemented in the CLR? I also get the feeling that the step to DP would incur an extra level of abstraction that might not model at all performant, would this be a fair comment? I have done some simple tests using F# and it all looks great, but am I missing something if the programs get more complex?

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• How to keep history of record updates in MySQL?

  - by Proxium

  I have to create a code in PHP that will allow me to keep the history of record updates in MySQL database so I can find by date an old revision. Here is the example of what I actualy want to achive: http://en.wikipedia.org/w/index.php?title=Tunisia&action=history The data are mostly Numbers that we record about the company for generating reports and to extract indices. I plan to use codeigniter for it's simplicity and I'm looking for idea about a framework or an opensource project that use the same approche to keep history of modifications in the database.

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• A specific string format with a number and character together represeting a certain item

  - by sil3nt

  Hello there, I have a string which looks like this "a 3e,6s,1d,3g,22r,7c 3g,5r,9c 19.3", how do I go through it and extract the integers and assign them to its corresponding letter variable?. (i have integer variables d,r,e,g,s and c). The first letter in the string represents a function, "3e,6s,1d,3g,22r,7c" and "3g,5r,9c" are two separate containers . And the last decimal value represents a number which needs to be broken down into those variable numbers. my problem is extracting those integers with the letters after it and assigning them into there corresponding letter. and any number with a negative sign or a space in between the number and the letter is invalid. How on earth do i do this?

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• can lapply not modify variables in a higher scope

  - by stevejb

  I often want to do essentially the following: mat <- matrix(0,nrow=10,ncol=1) lapply(1:10, function(i) { mat[i,] <- rnorm(1,mean=i)}) But, I would expect that mat would have 10 random numbers in it, but rather it has 0. (I am not worried about the rnorm part. Clearly there is a right way to do that. I am worry about affecting mat from within an anonymous function of lapply) Can I not affect matrix mat from inside lapply? Why not? Is there a scoping rule of R that is blocking this?

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• MS ACCESS: How can i count distinct value using access query?

  - by Sadat

  here is the current complex query given below. SELECT DISTINCT Evaluation.ETCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.TVenue, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Answer.QCode, Answer.Answer, Count(Answer.Answer) AS [Count], Questions.SL, Questions.Question FROM ((Evaluation INNER JOIN Training ON Evaluation.ETCode=Training.TCode) INNER JOIN Answer ON Evaluation.ECode=Answer.ECode) INNER JOIN Questions ON Answer.QCode=Questions.QCode GROUP BY Evaluation.ETCode, Answer.QCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.Tvenue, Answer.Answer, Questions.Question, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Questions.SL ORDER BY Answer.QCode, Answer.Answer; There is an another column Training.TCode. I need to count distinct Training.TCode, can anybody help me? If you need more information please let me know

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• php nl2br limit x amount

  - by Joshua Anderson

  Hi this is fairly simple I want to know how to use nl2br(); in php, but limit the amount of <br/>'s that are allowed at one time. //For Example: A user enters hi Im a jerk and made 16 more lines. or I could make as many as i want Is there anyway to have php limit the <br/>'s to no more than x amount of numbers at at time so if we only allowed 4 <br>'s at a time the output would be hi Im a jerk I tried to make 9 lines and it made it 4

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• Best design for generating code from an AST?

  - by Sam Washburn

  I'm working on a pretty complex DSL that I want to compile down into a few high level languages. The whole process has been a learning experience. The compiler is written in java. I was wondering if anyone knew a best practice for the design of the code generator portion. I currently have everything parsed into an abstract syntax tree. I was thinking of using a template system, but I haven't researched that direction too far yet as I would like to hear some wisdom first from stack overflow. Thanks!

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• Executing <script> elements inserted with .innerHTML

  - by phidah

  I've got a script that inserts some content into an element using innerHTML. The content could for example be: <script type="text/javascript">alert('test');</script> <strong>test</strong> Problem is that the code inside the <script> tag doesn't get executed. I googled it a bit but there were no apparent solutions. If I inserted the content using jQuery $(element).append(content);the script parts got eval'd before being injected into the DOM. Has anyone got a snippet of code that executes all the <script> elements? The jQuery code was a bit complex so I couldn't really figure out how it was done.

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• If you are forced to use an Anemic domain model, where do you put your business logic and calculated

  - by Jess

  Our current O/RM tool does not really allow for rich domain models, so we are forced to utilize anemic (DTO) entities everywhere. This has worked fine, but I continue to struggle with where to put basic object-based business logic and calculated fields. Current layers: Presentation Service Repository Data/Entity Our repository layer has most of the basic fetch/validate/save logic, although the service layer does a lot of the more complex validation & saving (since save operations also do logging, checking of permissions, etc). The problem is where to put code like this: Decimal CalculateTotal(LineItemEntity li) { return li.Quantity * li.Price; } or Decimal CalculateOrderTotal(OrderEntity order) { Decimal orderTotal = 0; foreach (LineItemEntity li in order.LineItems) { orderTotal += CalculateTotal(li); } return orderTotal; } Any thoughts?

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• VS2010 always relinks the project

  - by Rob Walker

  I am migrating a complex mixed C++/.NET solution from VS2008 to VS2010. The upgraded solution works in VS2010, but the build system is always refereshing one C++/CLI assembly. It doesn't recompile anything, but the linker touches the file. The causes a ripple effect downstream in the build as a whole bunch of dependent then get rebuilt. Any ideas on how to find out why it thinks it needs to relink the file? I've turned on verbose build logging, but nothing stands out.

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• keep duplicate number records only - perl

  - by manu

  Hello I have one text string which is having some duplicate characters (FFGGHHJKL), these can be made unique by using the positive lookahead [perl script for the same$ perl -pe 's/(.)(?=.*?\1)//g']. (FFEEDDCCGG OUTPUT == FEDCG) My question is how to make it work on the numbers (Ex. 212 212 43 43 5689 6689 5689 71 81 === output should be 212 43 5689 6689 71 81) ? Also if we want to have only duplicate records to be given as the output from a file having n rows (212 212 43 43 5689 6689 5689 71 81 \n 66 66 67 68 69 69 69 71 71 52 ..\n .. .. \n... OUTPUT == 212 212 43 43 5689 5689 \n 66 66 69 69 69 71 71) then what should be done ? Thanks and regards -manu

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