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• Receiving DB update events in .NET from SQLite

  - by Dan Tao

  I've recently discovered the awesomeness of SQLite, specifically the .NET wrapper for SQLite at http://sqlite.phxsoftware.com/. Now, suppose I'm developing software that will be running on multiple machines on the same network. Nothing crazy, probably only 5 or 6 machines. And each of these instances of the software will be accessing an SQLite database stored in a file in a shared directory (is this a bad idea? If so, tell me!). Is there a way for each instance of the app to be notifiied if one instance updates the database file? One obvious way would be to use the FileSystemWatcher class, read the entire database into a DataSet, and then ... you know ... enumerate through the entire thing to see what's new ... but yeah, that seems pretty idiotic, actually. Is there such a thing as a provider of SQLite updates? Does this even make sense as a question? I'm also pretty much a newbie when it comes to ADO.NET, so I might be approaching the problem from the entirely wrong angle.

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• What are the most interesting equivalences arising from the Curry-Howard Isomorphism?

  - by Tom

  I came upon the Curry-Howard Isomorphism relatively late in my programming life, and perhaps this contributes to my being utterly fascinated by it. It implies that for every programming concept there exists a precise analogue in formal logic, and vice versa. Here's an "obvious" list of such analogies, off the top of my head: program/definition | proof type/declaration | proposition inhabited type | theorem function | implication function argument | hypothesis/antecedent function result | conclusion/consequent function application | modus ponens recursion | induction identity function | tautology non-terminating function | absurdity tuple | conjunction (and) disjoint union | exclusive disjunction (xor) parametric polymorphism | universal quantification So, to my question: what are some of the more interesting/obscure implications of this isomorphism? I'm no logician so I'm sure I've only scratched the surface with this list. For example, here are some programming notions for which I'm unaware of pithy names in logic: currying | "((a & b) => c) iff (a => (b => c))" scope | "known theory + hypotheses" And here are some logical concepts which I haven't quite pinned down in programming terms: primitive type? | axiom set of valid programs? | theory ? | disjunction (or)

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• Scrolling screen upward to expose TextView above keyboard

  - by Matt Winters

  I think I'm missing something obvious and would appreciate an answer. I have a view with a 2-section grouped tableView, each section having one row and a textView, the heights of the rows 335 and 140. This allows for a box with nicely rounded corners to type text into when the keyboard appears (140 height section) and when the keyboard is dismissed, a nice box to read more text (notes); most of the time, use is without the keyboard. I also added a toolbar at the bottom of the screen to scroll up above the keyboard. A button on the toolbar dismisses the keyboard. This last part works fine with the keyboard going up and down using a notification and the following code in a keyboardWillShow method: [UIView beginAnimations:@"showKeyboardAnimation" context:nil]; [UIView setAnimationDuration:0.50]; self.view.frame = CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y, self.view.frame.size.width, self.view.frame.size.height - 216); [UIView commitAnimations]; But with the above code, the 2 sections of the tableView remain unscrolled, only the toolbar and the keyboard move. With the following code (found both in previous posts), both the toolbar and the tableView sections move. [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.50]; CGRect rect = self.view.frame; rect.origin.y -= 216; self.view.frame = rect; [UIView commitAnimations]; Now I know that I have to tweak the numbers to get the everything as I want it but my first question is what is substantively different between the 2 sets of code that the sections move in the 2nd but not in the 1st? The toolbar also moves with the 2nd code. The second question is, am I going to be able to scroll the smaller height section from off the screen to above the keyboard while at the same time moving the toolbar up just 216? Thanks

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• Can SOTI's MobiControl software interfere with an ASP.Net web service?

  - by MusiGenesis

  We have a set of WinMo (5.0) devices running a .NET CF application that talks to an ASP.Net web service running on a server. The devices connect to the network either via ActiveSync through a networked PC or directly to the network via an Ethernet dongle. In our development environment, the communication between devices and web service is 100% reliable. In our production environment, the communications are failing erratically and unpredictably. Sometimes calls to the web service (even to a simple test call that just returns a boolean) begin failing every time on a particular device, with the error message "Could not establish connection to network." This is usually fixed by flip-flopping the selected combo box values on the SETTINGS | NETWORKS screen. Sometimes calls on a particular device begin failing with a generic "WebException" message. The fix for this problem (so far) is either to reset the device (i.e. reinstall the OS) or else it just can't be fixed on some devices. To the best of our knowledge, everything about the DEV and PROD systems are the same (same server and device specs). The most obvious difference to us is that the PROD devices are all controlled by SOTI's MobiControl (which is server-side software that communicates with a SOTI client application installed on each device), whereas our DEV environment does not have SOTI installed anywhere (obviously we should have it there as well - long story). Does anybody have any experience with SOTI MobiControl and/or know of any documented problems where SOTI interferes with other communication mechanisms on a device?

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• Question about functional OOP style in JavaScript

  - by valums

  I prefer to use functional OOP style for my code (similar to the module pattern) because it helps me to avoid the "new" keyword and all problems with the scope of "this" keyword in callbacks. But I've run into a few minor issues with it. I would like to use the following code to create a class. namespace.myClass = function(){ var self = {}, somePrivateVar1; // initialization code that would call // private or public methods privateMethod(); self.publicMethod(); // sorry, error here function privateMethod(){} self.publicMethod = function(){}; return self; } The problem is that I can't call public methods from my initialization code, as these functions are not defined yet. The obvious solution would be to create an init method, and call it before "return self" line. But maybe you know a more elegant solution? Also, how do you usually handle inheritance with this pattern? I use the following code, butI would like to hear your ideas and suggestions. namespace.myClass2 = function(){ var self = namespace.parentClass(), somePrivateVar1; var superMethod = self.someMethod; self.someMethod = function(){ // example shows how to overwrite parent methods superMethod(); }; return self; } Edit. For those who asked what are the reasons for choosing this style of OOP, you can look into following questions: http://stackoverflow.com/questions/1557386/prototypal-vs-functional-oop-in-javascript http://stackoverflow.com/questions/383402/is-javascript-s-new-keyword-considered-harmful

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• Reordering arguments using recursion (pro, cons, alternatives)

  - by polygenelubricants

  I find that I often make a recursive call just to reorder arguments. For example, here's my solution for endOther from codingbat.com: Given two strings, return true if either of the strings appears at the very end of the other string, ignoring upper/lower case differences (in other words, the computation should not be "case sensitive"). Note: str.toLowerCase() returns the lowercase version of a string. public boolean endOther(String a, String b) { return a.length() < b.length() ? endOther(b, a) : a.toLowerCase().endsWith(b.toLowerCase()); } I'm very comfortable with recursions, but I can certainly understand why some perhaps would object to it. There are two obvious alternatives to this recursion technique: Swap a and b traditionally public boolean endOther(String a, String b) { if (a.length() < b.length()) { String t = a; a = b; b = t; } return a.toLowerCase().endsWith(b.toLowerCase()); } Not convenient in a language like Java that doesn't pass by reference Lots of code just to do a simple operation An extra if statement breaks the "flow" Repeat code public boolean endOther(String a, String b) { return (a.length() < b.length()) ? b.toLowerCase().endsWith(a.toLowerCase()) : a.toLowerCase().endsWith(b.toLowerCase()); } Explicit symmetry may be a nice thing (or not?) Bad idea unless the repeated code is very simple ...though in this case you can get rid of the ternary and just || the two expressions So my questions are: Is there a name for these 3 techniques? (Are there more?) Is there a name for what they achieve? (e.g. "parameter normalization", perhaps?) Are there official recommendations on which technique to use (when)? What are other pros/cons that I may have missed?

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• Backreferences in lookbehind

  - by polygenelubricants

  Can you use backreferences in a lookbehind? Let's say I want to split wherever behind me a character is repeated twice. String REGEX1 = "(?<=(.)\\1)"; // DOESN'T WORK! String REGEX2 = "(?<=(?=(.)\\1)..)"; // WORKS! System.out.println(java.util.Arrays.toString( "Bazooka killed the poor aardvark (yummy!)" .split(REGEX2) )); // prints "[Bazoo, ka kill, ed the poo, r aa, rdvark (yumm, y!)]" Using REGEX2 (where the backreference is in a lookahead nested inside a lookbehind) works, but REGEX1 gives this error at run-time: Look-behind group does not have an obvious maximum length near index 8 (?<=(.)\1) ^ This sort of make sense, I suppose, because in general the backreference can capture a string of any length (if the regex compiler is a bit smarter, though, it could determine that \1 is (.) in this case, and therefore has a finite length). So is there a way to use a backreference in a lookbehind? And if there isn't, can you always work around it using this nested lookahead? Are there other commonly-used techniques?

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• https google urlshortener request missing body

  - by Peter

  Hi, Just trying to get the new API for the goo.gl URL shortening service working on my iPhone, following the instructions on http://code.google.com/apis/urlshortener/v1/getting_started.html I'm set up and the API is enabled etc., but when I send a request in the recommended format: POST https://www.googleapis.com/urlshortener/v1/url Content-Type: application/json {"longUrl": "http://www.google.com/"} I get an error returned. The error is exactly the one listed on that page in the errors section for if you haven't passed in a longURL param. This makes me think that I'm not setting up the body of the POST request properly. Here's the code if you have any pointers... NSString *longURLString=@"http://www.stackoverflow.com"; NSString *googlRequestString=@"https://www.googleapis.com/urlshortener/v1/url"; NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:[NSURL URLWithString:googlRequestString]]; [request setHTTPMethod:@"POST"]; [request addValue:@"application/json" forHTTPHeaderField:@"Content-Type:"]; NSString *bodyString=[NSString stringWithFormat:@"{\"longUrl\": \"%@\"}",longURLString]; [request setHTTPBody:[bodyString dataUsingEncoding:NSUTF8StringEncoding]]; NSURLResponse *theResponse; NSError *error=nil; NSData *receivedData=[NSURLConnection sendSynchronousRequest:request returningResponse:&theResponse error:&error]; NSString *receivedString=[[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding]; NSLog(@"Received data: %@",receivedString); [receivedString release]; The NSLog returns: Received data: { "error": { "errors": [ { "domain": "global", "reason": "required", "message": "Required", "locationType": "parameter", "location": "resource.longUrl" } ], "code": 400, "message": "Required" } } which is exactly what Google says you get if you have not passed a longUrl parameter.... My guess is I'm missing something very obvious here :-) P

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• Are there any radix/patricia/critbit trees for Python?

  - by Andrew Dalke

  I have about 10,000 words used as a set of inverted indices to about 500,000 documents. Both are normalized so the index is a mapping of integers (word id) to a set of integers (ids of documents which contain the word). My prototype uses Python's set as the obvious data type. When I do a search for a document I find the list of N search words and their corresponding N sets. I want to return the set of documents in the intersection of those N sets. Python's "intersect" method is implemented as a pairwise reduction. I think I can do better with a parallel search of sorted sets, so long as the library offers a fast way to get the next entry after i. I've been looking for something like that for some time. Years ago I wrote PyJudy but I no longer maintain it and I know how much work it would take to get it to a stage where I'm comfortable with it again. I would rather use someone else's well-tested code, and I would like one which supports fast serialization/deserialization. I can't find any, or at least not any with Python bindings. There is avltree which does what I want, but since even the pair-wise set merge take longer than I want, I suspect I want to have all my operations done in C/C++. Do you know of any radix/patricia/critbit tree libraries written as C/C++ extensions for Python? Failing that, what is the most appropriate library which I should wrap? The Judy Array site hasn't been updated in 6 years, with 1.0.5 released in May 2007. (Although it does build cleanly so perhaps It Just Works.)

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• Looking for examples of "real" uses of continuations

  - by Sébastien RoccaSerra

  I'm trying to grasp the concept of continuations and I found several small teaching examples like this one from the Wikipedia article: (define the-continuation #f) (define (test) (let ((i 0)) ; call/cc calls its first function argument, passing ; a continuation variable representing this point in ; the program as the argument to that function. ; ; In this case, the function argument assigns that ; continuation to the variable the-continuation. ; (call/cc (lambda (k) (set! the-continuation k))) ; ; The next time the-continuation is called, we start here. (set! i (+ i 1)) i)) I understand what this little function does, but I can't see any obvious application of it. While I don't expect to use continuations all over my code anytime soon, I wish I knew a few cases where they can be appropriate. So I'm looking for more explicitely usefull code samples of what continuations can offer me as a programmer. Cheers!

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• After Navigate2 Method returns S_OK Stuck at READYSTATE of READYSTATE_LOADING

  - by Stone Free

  I am working on a MFC Document View architecture application which has multiple documents and views and a tabbed window interface. I have been tasked with making an automatic switch to another tab on the press of the OK button in one of the other tabs. When the other tab is clicked on it uses a C++ wrapper over IWebBrowser2 to navigate to a specific web page. When this is done manually by clicking on the tab everything is fine and the webpage within the view loads successfully. In my first attempt at doing this the tab successfully switched in response to a call to AfxGetMainWnd()->SendMessageToDescendants(SOME_MESSAGE, ...); however by sending this windows message at the wrong point the application would crash once control returned because the chain of events caused the (modeless) dialog (*) that sent the message, to no longer exist. I then found the correct place to make the call, but now when the other tab is activated, it no longer displays the webpage as it should. To debug this problem I added code to check the READYSTATE in both the situation where it works and the situation where it does not. When the page fails to load (despite the call to Navigate2 returning S_OK), the READYSTATE just stays at READYSTATE_LOADING. Unfortunately now I am to many edits away from when I had it partially working. I have added TRACE statements to the most obvious events such as OnSetFocus, CView::OnActivateView but all traces come out in the same order despite the behaviour being different * hosted in the view

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• Nhibernate/Hibernate, lookup tables and object design

  - by Simon G

  Hi, I've got two tables. Invoice with columns CustomerID, InvoiceDate, Value, InvoiceTypeID (CustomerID and InvoiceDate make up a composite key) and InvoiceType with InvoiceTypeID and InvoiceTypeName columns. I know I can create my objects like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceType InvoiceType { get; set; } } public class InvoiceType { public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } So the generated sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice WHERE CustomerID = x AND InvoiceDate = y SELECT InvoiceTypeID, InvoiceTypeName FROM InvoiceType WHERE InvoiceTypeID = z But rather that having two select queries executed to retrieve the data I would rather have one. I would also like to avoid using child object for simple lookup lists. So my object would look something like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } And my sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice INNER JOIN InvoiceType ON Invoice.InvoiceTypeID = InvoiceType.InvoiceTypeID WHERE CustomerID = x AND InvoiceDate = y My question is how do I create the mapping for this? I've tried using join but this tried to join using CustomerID and InvoiceDate, am I missing something obvious? Thanks

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• Using PHP to store results of a post request

  - by Paul M

  Im currently working with an API which requires we send our collection details in xml to their server using a post request. Nothing major there but its not working, so I want to output the sent xml to a txt file so I can look at actually whats being sent!! Instead of posting to the API im posting to a document called target, but the xml its outputting its recording seems to be really wrong. Here is my target script, note that the posting script posts 3 items, so the file being written should have details of each post request one after the other. <?php error_reporting(E_ALL); ini_set('display_errors', 1); // get the request data... $payload = ''; $fp = fopen('php://input','r'); $output_file = fopen('output.txt', 'w'); while (!feof($fp)) { $payload .= fgets($fp); fwrite($output_file, $payload); } fclose($fp); fclose($output_file); ?> I also tried the following, but this just recorded the last post request so only 1 collection item was recorded in the txt file, instead of all 3 output_file = fopen('output.txt', 'w'); while (!feof($fp)) { $payload .= fgets($fp); } fwrite($output_file, $payload); fclose($fp); fclose($output_file); I know im missing something really obvious, but ive been looking at this all morning!

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• Force Oracle error on fetch

  - by Dan

  I am trying to debug a strange behavior in my application. In order to do so, I need to reproduce a scenario where an SQL SELECT query will throw an error, but only while actually fetching from the cursor, not while executing the query itself. Can this be done? Any error will do, but ORA-01722: invalid number seems like the obvious one to try. I created a table with the follwing: KEYCOL INTEGER PRIMARY KEY OTHERCOL VARCHAR2(100) I then created a few hundred rows with unique values for the primary key and the value l for the othercol. I then ran a SELECT * query, picked a row somewhere in the middle, and updated it to the string abcd. I ran the query SELECT KEYCOL, TO_NUMBER(OTHERCOL) FROM SOMETABLE hoping to get some rows of good data an then an error later. But I keep getting ORA-01722: invalid number on the execute step itself. I have gotten this behavior programmatically using ADO (with server-side cursor) and JDBC, as well as from PL/SQL Developer. How can I get the result I'm looking for? thanks Edit - meant to add, when using ADO, I am only calling Command.Execute. I am not creating or opening a Recordset.

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• dynamic date formats in eyecon's Bootstrap Datepicker

  - by Jennifer Michelle

  I need to update my datepickers' date format (mm.dd.yyyy etc) using a select box. I am currently using Eyecon's Bootstrap Datepicker because it had the smallest files size that I could find (8k minified), and includes the date formats I need. I also tried to trigger date format changes in several other datepickers without any success. Fiddle: http://jsfiddle.net/Yshy7/8/ Is there an obvious way to trigger a change from the select box to the datepickers? //date format var dateFormat = $('#custom_date_format').val() || "mm/dd/yyyy"; $('#custom_date_format').change(function() { var dateFormat = $(this).val(); }); //start and end dates var nowTemp = new Date(); var now = new Date(nowTemp.getFullYear(), nowTemp.getMonth(), nowTemp.getDate(), 0, 0, 0, 0); var checkin = $('.j-start-date').datepicker({ format: dateFormat, onRender: function(date) { //return date.valueOf() < now.valueOf() ? 'disabled' : ''; } }).on('changeDate', function(ev) { if (ev.date.valueOf() > checkout.date.valueOf()) { var newDate = new Date(ev.date) newDate.setDate(newDate.getDate()); checkout.setValue(newDate); } checkin.hide(); $('.j-end-date')[0].focus(); }).data('datepicker'); var checkout = $('.j-end-date').datepicker({ format: dateFormat, onRender: function(date) { return date.valueOf() <= checkin.date.valueOf() ? 'disabled' : ''; } }).on('changeDate', function(ev) { checkout.hide(); }).data('datepicker');

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• Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

  - by James D

  Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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• CSRF Protection in AJAX Requests using MVC2

  - by mnemosyn

  The page I'm building depends heavily on AJAX. Basically, there is just one "page" and every data transfer is handled via AJAX. Since overoptimistic caching on the browser side leads to strange problems (data not reloaded), I have to perform all requests (also reads) using POST - that forces a reload. Now I want to prevent the page against CSRF. With form submission, using Html.AntiForgeryToken() works neatly, but in AJAX-request, I guess I will have to append the token manually? Is there anything out-of-the box available? My current attempt looks like this: I'd love to reuse the existing magic. However, HtmlHelper.GetAntiForgeryTokenAndSetCookie is private and I don't want to hack around in MVC. The other option is to write an extension like public static string PlainAntiForgeryToken(this HtmlHelper helper) { // extract the actual field value from the hidden input return helper.AntiForgeryToken().DoSomeHackyStringActions(); } which is somewhat hacky and leaves the bigger problem unsolved: How to verify that token? The default verification implementation is internal and hard-coded against using form fields. I tried to write a slightly modified ValidateAntiForgeryTokenAttribute, but it uses an AntiForgeryDataSerializer which is private and I really didn't want to copy that, too. At this point it seems to be easier to come up with a homegrown solution, but that is really duplicate code. Any suggestions how to do this the smart way? Am I missing something completely obvious?

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• Cucumber could not find table; but its there. What is going on?

  - by JZ

  I'm working with cucumber and I'm running into difficulties. When I run "cucumber features", I am met with errors, cucumber is unable to find my requests table. What obvious mistake am I making? Thank you in advance! Bash: justin-zollarss-mac-pro:conversion justinz$ cucumber features Using the default profile... /Users/justinz/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be removed on or after August 2010. Use #requirement F-- (::) failed steps (::) Could not find table 'requests' (ActiveRecord::StatementInvalid) ./features/article_steps.rb:3 ./features/article_steps.rb:2:in `each' ./features/article_steps.rb:2:in `/^I have requests named (.+)$/' features/manage_articles.feature:7:in `Given I have requests named Foo, Bar' Failing Scenarios: cucumber features/manage_articles.feature:6 # Scenario: Conversion 1 scenario (1 failed) 3 steps (1 failed, 2 skipped) 0m0.154s justin-zollarss-mac-pro:conversion justinz$ Manage_articles.feature: Feature: Manage Articles In order to make sales As a customer I want to make conversions Scenario: Conversion Given I have requests named Foo, Bar When I go to the list of customers Then I should see a new "customer" Article_steps.rb: Given /^I have requests named (.+)$/ do |firsts| firsts.split(', ').each do |first| Request.create!(:first => first) pending # express the regexp above with the code you wish you had end end Then /^I should see a new "([^"]*)"$/ do |arg1| pending # express the regexp above with the code you wish you had end DB schema: ActiveRecord::Schema.define(:version => 20100528011731) do create_table "requests", :force => true do |t| t.string "institution" t.string "website" t.string "type" t.string "users" t.string "first" t.string "last" t.string "jobtitle" t.string "phone" t.string "email" t.datetime "created_at" t.datetime "updated_at" end end

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• Sqlite3 "chained" query

  - by Arrieta

  I need to create a configuration file from a data file that looks as follows: MAN1_TIME '01-JAN-2010 00:00:00.0000 UTC' MAN1_RX 123.45 MAN1_RY 123.45 MAN1_RZ 123.45 MAN1_NEXT 'MAN2' MAN2_TIME '01-MAR-2010 00:00:00.0000 UTC' MAN2_RX 123.45 [...] MAN2_NEXT 'MANX' [...] MANX_TIME [...] This file describes different "legs" of a trajectory. In this case, MAN1 is chained to MAN2, and MAN2 to MANX. In the original file, the chains are not as obvious (i.e., they are non-sequential). I've managed to read the file and store in an Sqlite3 database (I'm using the Python interface). The table is stored with three columns: Id, Par, and Val; for instance, Id='MAN1', Par='RX', and Val='123.45'. I'm interested in querying such database for obtaining the information related to 'n' legs. In English, that would be: "Select RX,RY,RZ for the next five legs starting on MAN1" So the query would go to MAN1, retrieve RX, RY, RZ, then read the parameter NEXT and go to that Id, retrieve RX, RY, RZ; read the parameter NEXT; go to that one ... like this five times. How can I pass such query with "dynamic parameters"? Thank you.

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• Best pratice: How do I implement a list that can be rendered both server-side and client-side?

  - by André Pena

  Technologies involved: ASP.NET Web-forms Javascript (jQuery for instance) Case To make it clearer let's give the Stackoverflow authors list as an example. This list can be manipulated at client-side. I can search, page and so forth. So obviously we would need to call jQuery.ajax to retrieve the HTML of each page given a search. Alright. Now this leaves me with the first question: What is the best way to render the response for the jQuery.ajax at server-side? I can't use templates I suppose, so the most obvious solution I think is to create the HTML tags as server-controls and render them as the result of an ASHX request? Is this is best approach? Nice. That solved we have yet another problem: When the user first enters the Authors List the first list page should already come from the server completely rendered alright? Of course we could render the first page as well as an ajax call but I don't think it's better. This time I CAN use templates to render the list but this template couldn't be reused in case 1. What do I do? Now the final question: Now we have 2 rendering strategies: 1) Client and 2) Server. How do I reuse code for the 2 renderings? What are the best pratices for solving these problems?

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• Does this use of Monitor.Wait/Pulse have a race condition?

  - by jw

  I have a simple producer/consumer scenario, where there is only ever a single item being produced/consumed. Also, the producer waits for the worker thread to finish before continuing. I realize that kind of obviates the whole point of multithreading, but please just assume it really needs to be this way (: This code doesn't compile, but I hope you get the idea: // m_data is initially null // This could be called by any number of producer threads simultaneously void SetData(object foo) { lock(x) // Line A { assert(m_data == null); m_data = foo; Monitor.Pulse(x) // Line B while(m_data != null) Monitor.Wait(x) // Line C } } // This is only ever called by a single worker thread void UseData() { lock(x) // Line D { while(m_data == null) Monitor.Wait(x) // Line E // here, do something with m_data m_data = null; Monitor.Pulse(x) // Line F } } Here is the situation that I am not sure about: Suppose many threads call SetData() with different inputs. Only one of them will get inside the lock, and the rest will be blocked on Line A. Suppose the one that got inside the lock sets m_data and makes its way to Line C. Question: Could the Wait() on Line C allow another thread at Line A to obtain the lock and overwrite m_data before the worker thread even gets to it? Supposing that doesn't happen, and the worker thread processes the original m_data, and eventually makes its way to Line F, what happens when that Pulse() goes off? Will only the thread waiting on Line C be able to get the lock? Or will it be competing with all the other threads waiting on Line A as well? Essentially, I want to know if Pulse()/Wait() communicate with each other specially "under the hood" or if they are on the same level with lock(). The solution to these problems, if they exist, is obvious of course - just surround SetData() with another lock - say, lock(y). I'm just curious if it's even an issue to begin with.

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• jquery slide to attribute with specific data attribute value

  - by Alex M

  Ok, so I have the following nav with absolute urls: <ul class="nav navbar-nav" id="main-menu"> <li class="first active"><a href="http://example.com/" title="Home">Home</a></li> <li><a href="http://example.com/about.html" title="About">About</a></li> <li><a href="http://example.com/portfolio.html" title="Portfolio">Portfolio</a></li> <li class="last"><a href="example.com/contact.html" title="Contact">Contact</a></li> </ul> and then articles with the following data attributes: <article class="row page" id="about" data-url="http://example.com/about.html"> <div class="one"> </div> <div class="two" </div> </article> and when you click the link in the menu I would like to ignore the fact it is a hyperlink and slide to the current article based on its attribute data-url. I started with what I think is the obvious: $('#main-menu li a').on('click', function(event) { event.preventDefault(); var pageUrl = $(this).attr('href'); )}; and have tried find and animate but then I don't know how to reference the article with data-url="http://example.com/about.html". Any help would be most appreciated. Thanks

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• Small-o(n^2) implementation of Polynomial Multiplication

  - by AlanTuring

  I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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• iPhone accelerometer:didAccelerate: seems to not get called while I am running a loop

  - by AJ

  An accelerometer related question. (Sorry the formatting may not look right, its the first time I am using this site). I got the accelerometer working as expected using the standard code UIAccelerometer *accel = [UIAccelerometer sharedAccelerometer]; accel.delegate = self; accel.updateInterval = 0.1; //I also tried other update values I use NSLog to log every time the accelerometer:didAccelerate: method in my class is called. The function gets called as expected and everything works fine till here. However, when I run a loop, the above method doesn't seem to get called. Something like this float firstAccelValue = globalAccel; //this is the x-accel value (stored in a global by the above method) float nextAccelValue = firstAccelValue; while (nextAccelValue == firstAccelValue){ //do something nextAccelValue = globalAccel; // note globalAccel is updated by the accelerometer method } The above loop never exits, expectedly since the accelerometer:didAccelerate: method is not getting called, and hence globalAccel never changes value. If I use a fixed condition to break the while loop, I can see that after the loop ends, the method calls work fine again. Am I missing something obvious here? Or does the accelerometer method not fire when certain processing is being done? Any help would be greatly appreciated! Thanks!

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• Is there a standard mapping between JSON and Protocol Buffers?

  - by Daniel Earwicker

  From a comment on the announcement blog post: Regarding JSON: JSON is structured similarly to Protocol Buffers, but protocol buffer binary format is still smaller and faster to encode. JSON makes a great text encoding for protocol buffers, though -- it's trivial to write an encoder/decoder that converts arbitrary protocol messages to and from JSON, using protobuf reflection. This is a good way to communicate with AJAX apps, since making the user download a full protobuf decoder when they visit your page might be too much. It may be trivial to cook up a mapping, but is there a single "obvious" mapping between the two that any two separate dev teams would naturally settle on? If two products supported PB data and could interoperate because they shared the same .proto spec, I wonder if they would still be able to interoperate if they independently introduced a JSON reflection of the same spec. There might be some arbitrary decisions to be made, e.g. should enum values be represented by a string (to be human-readable a la typical JSON) or by their integer value? So is there an established mapping, and any open source implementations for generating JSON encoder/decoders from .proto specs?

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