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• What is a mantainable way of saving "star rating" in a database?

  - by Montecristo

  I'll use the jQuery plugin for presenting the user with a nice interface The request is to display 5 stars, up to a total score of 10 (2 points per star). By now I thought about using 7/10 as a format for that value, but what if at some point in the future I'll receive a request like We would like to give users more choice, let's increase the total score to 20 (so that each star contributes with a maximum of 4 points) I'll end up with a table with mixed values for the "star rating" column: some will be like 7/10 while others will be like 14/20. Is it ok for you to have this difference in the database and deal with it in the logic layer to have it consistent? Or is preferred another way so that querying the table will not result in inconsistent results outside the application? Maybe floating point values could help me, is it better to store that value as a number less than or equal to one? So in each of the two examples the resulting value stored in the database would be 0,7, as a number, not a varchar, which can be queried also outside the application. What do you think?

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• SELECT set of most recent id, amount FROM table, where id occurs many times

  - by Jon Cram

  I have a table recording the amount of data transferred by a given service on a given date. One record is entered daily for a given service. I'd like to be able to retrieve the most recent amount for a set of services. Example data set: serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 2 | 14 | 2010-04-11 3 | 9 | 2010-04-11 1 | 6 | 2010-04-10 2 | 5 | 2010-04-10 3 | 22 | 2010-04-10 4 | 17 | 2010-04-19 Desired response (service ids 1,2,3): serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 3 | 9 | 2010-04-11 Desired response (service ids 2, 4): serviceId | amount | date ------------------------------- 2 | 11 | 2010-04-12 4 | 17 | 2010-04-19 This retrieves the equivalent as running the following once per serviceId: SELECT serviceId, amount, date FROM table WHERE serviceId = <given serviceId> ORDER BY date DESC LIMIT 0,1 I understand how I can retrieve the data I want in X queries. I'm interested to see how I can retrieve the same data using either a single query or at the very least less than X queries. I'm very interested to see what might be the most efficient approach. The table currently contains 28809 records. I appreciate that there are other questions that cover selecting the most recent set of records. I have examined three such questions but have been unable to apply the solutions to my problem.

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• SQL Compact performance on device

  - by Ben M

  My SQL Compact database is very simple, with just three tables and a single index on one of the tables (the table with 200k rows; the other two have less than a hundred each). The first time the .sdf file is used by my Compact Framework application on the target Windows Mobile device, the system hangs for well over a minute while "something" is done to the database: when deployed, the DB is 17 megabytes, and after this first usage, it balloons to 24 megs. All subsequent usage is pretty fast, so I'm assuming there's some sort of initialization / index building going on during this first usage. I'd rather not subject the user to this delay, so I'm wondering what this initialization process is and whether it can be performed before deployment. For now, I've copied the "initialized" database back to my desktop for use in the setup project, but I'd really like to have a better answer / solution. I've tried "full compact / repair" in the VS Database Properties dialog, but this made no difference. Any ideas? For the record, I should add that the database is only read from by the device application -- no modifications are made by that code.

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• WPF: How do I bind a Control to a formula composed of several dependency properties?

  - by Pablo

  Hi all, I'm working on Expression Blend and I'm currently designing a custom control which has a Grid with 5 rows inside, and also has two Dependency properties: "Value", and "Maximum". Three of the rows have fixed height, and what I'm trying to do is set the remaining rows height to "Value/Maximum" and "1-Value/Maximum" respectively. How do I go and do that? When I set the height to "Value" it seems to react, but when I go and set it to "Value/Maximum" it stops working. I'm still a bit new around WPF, so there must be another way to achieve what I'm intending, but after searching I couln't find my problem elsewhere. Code: <Grid x:Name="LayoutRoot" Width="Auto" Background="Transparent"> <Grid.RowDefinitions> <RowDefinition Height="32"/> <RowDefinition Height="{Binding Path=(Value/Maximum), ElementName=UserControl, Mode=Default}"/> <RowDefinition Height="16"/> <RowDefinition Height="{Binding Path=(1-Value/Maximum), ElementName=UserControl, Mode=Default}"/> <RowDefinition Height="32"/> </Grid.RowDefinitions> (...) By the way, Value is always a not negative double less than or equal to Maximum; so the result of the division will be number between 0.0 a 1.0. I want a "star" instead of "pixel" row height.

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• Python vs all the major professional languages [closed]

  - by Matt

  I've been reading up a lot lately on comparisons between Python and a bunch of the more traditional professional languages - C, C++, Java, etc, mainly trying to find out if its as good as those would be for my own purposes. I can't get this thought out of my head that it isn't good for 'real' programming tasks beyond automation and macros. Anyway, the general idea I got from about two hundred forum threads and blog posts is that for general, non-professional-level progs, scripts, and apps, and as long as it's a single programmer (you) writing it, a given program can be written quicker and more efficiently with Python than it could be with pretty much any other language. But once its big enough to require multiple programmers or more complex than a regular person (read: non-professional) would have any business making, it pretty much becomes instantly inferior to a million other languages. Is this idea more or less accurate? (I'm learning Python for my first language and want to be able to make any small app that I want, but I plan on learning C eventually too, because I want to get into driver writing eventually. So I've been trying to research each ones strengths and weaknesses as much as I can.) Anyway, thanks for any input

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• Freetype2 (error-)return value documentation

  - by Awaki

  In short, I'm looking for documentation that would limit the error situations to check for after a Freetype library function failed, much like the OpenGL and Win32 APIs document the error codes generated by their respective functions. I can't seem to find such documentation though, so I was wondering how to best handle translation of Freetype errors to typed exceptions. Background: I am currently in the process of implementing font-rendering capability (using Freetype) for my GUI framework, which makes strong use of typed exceptions to indicate error situations. However, the Freetype docs seem to completely omit what errors can be expected from what functions. That, if such documentation does indeed not exist, would basically leave me with two options: either guessing which errors make sense for a certain Freetype function (obviously prone to mistakes on my part), or considering every error code for translation into appropriate exceptions (less verbose since I would have to write the translation only once). Performance isn't really critical in the code that calls the Freetype library, so even the latter option would probably be acceptable, but surely there must be some kind of documentation on which library calls may return what Freetype error? Is there any such documentation which I just somehow managed to not find? Should I go the route of generically expecting every error code for translation? Or are there other ways to approach this problem? By the way, I wanted to avoid introducing some kind of generic FreetypeException (containing a description of the Freetype error) since I intended to completely hide what libraries I'm using (not from a legal point-of-view, mind you), but I guess I can be convinced to do this anyway if the consensus is that it would be the best option. I don't think it matters for this question, but I'm writing in C++.

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• How can I change jtable height at runtime

  - by wniroshan

  I hava a JFrame with multiple JPanels of similar width aligned one below other. I use one of these JPanels to display a JTable which is the last JPanel of the lot. This JPanel has a JScrollpane as a child component. This is where I try to add my table dynamically. Initial height of this JScrollpane is set to 40. I designed above template using Netbeans 6.8 Now I'm trying to add the table to the JPanel. When a button is pressed below code snippet is called. The class which includes this code extends javax.swing.JFrame class. I am expecting below code would adjust table height according to the row count and display the table. SearchTable = new JTable(RowData, DisplayNames) { @Override public boolean isCellEditable(int rowIndex, int vColIndex) { return false; } }; // if row count is less than 10 then display all the rows without a scroll bar if (SearchTable.getRowCount() < 10) { pnl_tblpanel.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (SearchTable.getRowCount() + 4))); scr_tblholder.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (SearchTable.getRowCount() + 4))); } else {// if row count is more than 10 display first 10 rows and add a scroll bar pnl_tblpanel.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (10 + 2))); scr_tblholder.setAutoscrolls(true); } //pnl_tblpanel.add(scr_tblholder); scr_tblholder.setViewportView(SearchTable); //pnl_tblpanel.repaint(); pnl_tblpanel.validate(); this.validate(); //this.repaint(); pnl_tblpanel.setVisible(true); this.pack(); The table displays, but the table height is not changed according to the row count. It stays its default value. I have been trying many combinations of validate and repaint but nothing worked. (More in desperation) Can anyone shed some light on this Thank you

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• Error in bisection method code in Matlab

  - by Amanda Collins

  I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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• Retain numerical precision in an R data frame?

  - by David

  When I create a dataframe from numeric vectors, R seems to truncate the value below the precision that I require in my analysis: data.frame(x=0.99999996) returns 1 (see update 1) I am stuck when fitting spline(x,y) and two of the x values are set to 1 due to rounding while y changes. I could hack around this but I would prefer to use a standard solution if available. example Here is an example data set d <- data.frame(x = c(0.668732936336141, 0.95351462456867, 0.994620622127435, 0.999602102672081, 0.999987126195509, 0.999999955814133, 0.999999999999966), y = c(38.3026509783688, 11.5895099585560, 10.0443344234229, 9.86152339768516, 9.84461434575695, 9.81648333804257, 9.83306725758297)) The following solution works, but I would prefer something that is less subjective: plot(d$x, d$y, ylim=c(0,50)) lines(spline(d$x, d$y),col='grey') #bad fit lines(spline(d[-c(4:6),]$x, d[-c(4:6),]$y),col='red') #reasonable fit Update 1 Since posting this question, I realize that this will return 1 even though the data frame still contains the original value, e.g. > dput(data.frame(x=0.99999999996)) returns structure(list(x = 0.99999999996), .Names = "x", row.names = c(NA, -1L), class = "data.frame") Update 2 After using dput to post this example data set, and some pointers from Dirk, I can see that the problem is not in the truncation of the x values but the limits of the numerical errors in the model that I have used to calculate y. This justifies dropping a few of the equivalent data points (as in the example red line).

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• Excel - Variable number of leading zeros in variable length numbers?

  - by daltec

  The format of our member numbers has changed several times over the years, such that 00008, 9538, 746, 0746, 00746, 100125, and various other permutations are valid, unique and need to be retained. Exporting from our database into the custom Excel template needed for a mass update strips the leading zeros, such that 00746 and 0746 are all truncated to 746. Inserting the apostrophe trick, or formatting as text, does not work in our case, since the data seems to be already altered by the time we open it in Excel. Formatting as zip won't work since we have valid numbers less than five digits in length that cannot have zeros added to them. And I am not having any luck with "custom" formatting as that seems to require either adding the same number of leading zeros to a number, or adding enough zeros to every number to make them all the same length. Any clues? I wish there was some way to set Excel to just take what it's given and leave it alone, but that does not seem to be the case! I would appreciate any suggestions or advice. Thank you all very much in advance!

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• gcc compilations (sometimes) result in cpu underload

  - by confusedCoder

  I have a larger C++ program which starts out by reading thousands of small text files into memory and storing data in stl containers. This takes about a minute. Periodically, a compilation will exhibit behavior where that initial part of the program will run at about 22-23% CPU load. Once that step is over, it goes back to ~100% CPU. It is more likely to happen with O2 flag turned on but not consistently. It happens even less often with the -p flag which makes it almost impossible to profile. I did capture it once but the gprof output wasn't helpful - everything runs with the same relative speed just at low cpu usage. I am quite certain that this has nothing to do with multiple cores. I do have a quad-core cpu, and most of the code is multi-threaded, but I tested this issue running a single thread. Also, when I run the problematic step in multiple threads, each thread only runs at ~20% CPU. I apologize ahead of time for the vagueness of the question but I have run out of ideas as to how to troubleshoot it further, so any hints might be helpful. UPDATE: Just to make sure it's clear, the problematic part of the code does sometimes (~30-40% of the compilations) run at 100% CPU, so it's hard to buy the (otherwise reasonable) argument that I/O is the bottleneck

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• Many users, many cpus, no delays. Good for cloud?

  - by Eric

  I wish to set up a CPU-intensive time-important query service for users on the internet. A usage scenario is described below. Is cloud computing the right way to go for such an implementation? If so, what cloud vendor(s) cater to this type of application? I ask specifically, in terms of: 1) pricing 2) latency resulting from: - slow CPUs, instance creations, JIT compiles, etc.. - internal management and communication of processes inside the cloud (e.g. a queuing process and a calculation process) - communication between cloud and end user 3) ease of deployment A usage scenario I am expecting is: - A typical user sends a query (XML of size around 1K) once every 30 seconds on average. - Each query requires a numerical computation of average time 0.2 sec and max time 1 sec on a 1 GHz Pentium. The computation requires no data other than the query itself and is performed by the same piece of code each time. - The delay a user experiences between sending a query and receiving a response should be on average no more than 2 seconds and in general no more than 5 seconds. - A background save to a DB of the response should occur (not time critical) - There can be up to 30000 simultaneous users - i.e., on average 1000 queries a second, each requiring an average 0.2 sec calculation, so that would necessitate around 200 CPUs. Currently I'm look at GAE Java (for quicker deployment and less IT hassle) and EC2 (Speed and price optimization) as options. Where can I learn more about the right way to set ups such a system? past threads, different blogs, books, etc.. BTW, if my terminology is wrong or confusing, please let me know. I'd greatly appreciate any help.

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• Storing an encrypted cookie with Rails

  - by J. Pablo Fernández

  I need to store a small piece of data (less than 10 characters) in a cookie in Rails and I need it to be secure. I don't want anybody being able to read that piece of data or injecting their own piece of data (as that would open up the app to many kinds of attacks). I think encrypting the contents of the cookie is the way to go (should I also sign it?). What is the best way to do it? Right now I'm doing this, which looks secure, but many things looked secure to people that knew much more than I about security and then it was discovered it wasn't really secure. I'm saving the secret in this way: encryptor = ActiveSupport::MessageEncryptor.new(Example::Application.config.secret_token) cookies[:secret] = { :value => encryptor.encrypt(secret), :domain => "example.com", :secure => !(Rails.env.test? || Rails.env.development?) } and then I'm reading it like this: encryptor = ActiveSupport::MessageEncryptor.new(Example::Application.config.secret_token) secret = encryptor.decrypt(cookies[:secret]) Is that secure? Any better ways of doing it? Update: I know about Rails' session and how it is secure, both by signing the cookie and by optionally storing the contents of the session server side and I do use the session for what it is for. But my question here is about storing a cookie, a piece of information I do not want in the session but I still need it to be secure.

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• problem with a very simple tile based game

  - by newbieguy

  Hello, I am trying to create a pacman-like game. I have an array that looks like this: array: 1111111111111 1000000000001 1111110111111 1000000000001 1111111111111 1 = Wall, 0 = Empty space I use this array to draw tiles that are 16x16 in size. The Game character is 32x32. Initially I represented the character's position in array indexes, [1,1] etc. I would update his position if array[character.new_y][charater.new_x] == 0 Then I translated these array coordinates to pixels, [y*16, x*16] to draw him. He was lining up nicely, wouldn't go into walls, but I noticed that since I was updating him by 16 pixels each, he was moving very fast. I decided to do it in reverse, to store the game character's position in pixels instead, so that he could use less than 16 pixels per move. I thought that a simple if statement such as this: if array[(character.new_pixel_y)/16][(character.new_pixel_x)/16] == 0 would prevent him from going into walls, but unfortunately he eats a bit of the bottom and right side walls. Any ideas how would I properly translate pixel position to the array indexes? I guess this is something simple, but I really can't figure it out :(

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• Run multiple MySQL queries based on a series of ifs

  - by OldWest

  I am just getting started on this complex query I need to write and was hoping for any suggestions or feedback regarding table structure and the actual query itself.. I've already created my tables and populated test data, and now just trying to sort out how and what is possible within MySQL. Here is an outline of the problem: End result: Listing of rates based on specific queried criteria (see below): Age: [ 27 ] Spouse Age: [ 25 ] Num of Children: [ 3 ] Zip Code: [ 97128 ] The problem I am running into is each company that provides rates has a unique way of dealing with the rate. And I am looking for the best approach for multiple queries based on the company (one query with results for each company more or less all combined into one result set). Here are some facts: - Each company deals with zip code ranges which assist in the query result. - Each company has a different method of calculating the rate based on the Applicant, Spouse, Num of Children: Example, a) Company A determines rate by: Applicant + Spouse + Child(ren) = rate (age is pertinent to the applicant within a range). b) Company B determines the rate by total number of applicants like: 1, 2, 3, 4, 5, 6+ = rate (and age is ignored). First off, what would I call this type of query? Multiple nested query? And should I intertwine php within it to determine the If()s ... I apologize if this thread lacks sufficient data, so please tell me anything you would like to see.

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• Freeing ImageData when deleting a Canvas

  - by user578770

  I'm writing a XUL application using HTML Canvas to display Bitmap images. I'm generating ImageDatas and imporingt them in a canvas using the putImageData function : for(var pageIndex=0;pageIndex<100;pageIndex++){ this.img = imageDatas[pageIndex]; /* Create the Canvas element */ var imgCanvasTmp = document.createElementNS("http://www.w3.org/1999/xhtml",'html:canvas'); imgCanvasTmp.setAttribute('width', this.img.width); imgCanvasTmp.setAttribute('height', this.img.height); /* Import the image into the Canvas */ imgCanvasTmp.getContext('2d').putImageData(this.img, 0, 0); /* Use the Canvas into another part of the program (Commented out for testing) */ // this.displayCanvas(imgCanvasTmp,pageIndex); } The images are well imported but there seems to be a memory leak due to the putImageData function. When exiting the "for" loop, I would expect the memory allocated for the Canvas to be freed but, by executing the code without executing putImageData, I noticed that my program at the end use 100Mb less (my images are quite big). I came to the conclusion that the putImageData function prevent the garbage collector to free the allocated memory. Do you have any idea how I could force the garbage collector to free the memory? Is there any way to empty the Canvas? I already tried to delete the canvas using the delete operator or to use the clearRect function but it did nothing. I also tried to reuse the same canvas to display the image at each iteration but the amount of memory used did not changed, as if the image where imported without deleting the existing ones...

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• C# : How to round-off hours based on Minutes(hours+0 if min<30, hours+1 otherwise) ?

  - by infant programmer

  I need to round-off the hours based on the minutes in a dateTime variable. The condition is : if minutes are less than 30, then minutes must be set to zero and no changes to hours, Else if minutes =30, then hours must be set to hours+1 and minutes are again set to zero. Seconds are ignored. example: 11/08/2008 04:30:49 should become 11/08/2008 05:00:00 and 11/08/2008 04:29:49 should become 11/08/2008 04:00:00 I have written a Code which works perfectly fine, but just wanted to know a better method if could be written and also would appreciate alternative method(s). string date1 = "11/08/2008 04:30:49"; DateTime startTime; DateTime.TryParseExact(date1, "MM/dd/yyyy HH:mm:ss", null, System.Globalization.DateTimeStyles.None, out startTime); if (Convert.ToInt32((startTime.Minute.ToString())) > 29) { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); startTime = startTime.Add(TimeSpan.Parse("01:00:00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); } else { startTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}:{5}", startTime.Month.ToString(), startTime.Day.ToString(), startTime.Year.ToString(), startTime.Hour.ToString(), "00", "00")); Console.WriteLine("startTime is :: {0}", startTime.ToString("MM/dd/yyyy HH:mm:ss")); }

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• In Java, is there a performance gain in using interfaces for complex models?

  - by Gnoupi

  The title is hardly understandable, but I'm not sure how to summarize that another way. Any edit to clarify is welcome. I have been told, and recommended to use interfaces to improve performances, even in a case which doesn't especially call for the regular "interface" role. In this case, the objects are big models (in a MVC meaning), with many methods and fields. The "good use" that has been recommended to me is to create an interface, with its unique implementation. There won't be any other class implementing this interface, for sure. I have been told that this is better to do so, because it "exposes less" (or something close) to the other classes which will use methods from this class, as these objects are referring to the object from its interface (all public methods from the implementation being reproduced in the interface). This seems quite strange to me, as it seems like a C++ use to me (with header files). There I see the point, but in Java? Is there really a point in making an interface for such unique implementation? I would really appreciate some clarifications on the topic, so I could justify not following such kind of behavior, and the hassle it creates from duplicating all declarations. Edit: Plenty of valid points in most answers, I'm wondering if I won't switch this question for a community wiki, so we can regroup these points in more structured answers.

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• Timing issues with playback of the HTML5 Audio API

  - by pat

  I'm using the following code to try to play a sound clip with the HTML5 Audio API: HTMLAudioElement.prototype.playClip = function(startTime, stopTime) { this.stopTime = stopTime; this.currentTime = startTime; this.play(); $(this).bind('timeupdate', function(){ if (this.ended || this.currentTime >= stopTime) { this.pause(); $(this).unbind('timeupdate'); } }); } I utilize this new playClip method as follows. First I have a link with some data attributes: <a href=# data-stop=1.051 data-start=0.000>And then I was thinking,</a> And finally this bit of jQuery which runs on $(document).ready to hook up a click on the link with the playback: $('a').click(function(ev){ $('a').click(function(ev){ var start = $(this).data('start'), stop = $(this).data('stop'), audio = $('audio').get(0), $audio = $(audio); ev.preventDefault(); audio.playClip(start,stop); }) This approach seems to work, but there's a frustrating bug: sometimes, the playback of a given clip plays beyond the correct data-stop time. I suspect it could have something to do with the timing of the timeupdate event, but I'm no JS guru and I don't know how to begin debugging the problem. Here are a few clues I've gathered: The same behavior appears to come up in both FF and Chrome. The playback of a given clip actually seems to vary a bit -- if I play the same clip a couple times in a row, it may over-play a different amount of time on each playing. Is the problem here the inherent accuracy of the Audio API? My app needs milliseconds. Is there a problem with the way I'm using jQuery to bind and unbind the timeupdate event? I tried using the jQuery-less approach with addEventListener but I couldn't get it to work. Thanks in advance, I would really love to know what's going wrong.

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• C++ Iterator Pipelining Designs

  - by Kirakun

  Suppose we want to apply a series of transformations, int f1(int), int f2(int), int f3(int), to a list of objects. A naive way would be SourceContainer source; TempContainer1 temp1; transform(source.begin(), source.end(), back_inserter(temp1), f1); TempContainer2 temp2; transform(temp1.begin(), temp1.end(), back_inserter(temp2), f2); TargetContainer target; transform(temp2.begin(), temp2.end(), back_inserter(target), f3); This first solution is not optimal because of the extra space requirement with temp1 and temp2. So, let's get smarter with this: int f123(int n) { return f3(f2(f1(n))); } ... SourceContainer source; TargetContainer target; transform(source.begin(), source.end(), back_inserter(target), f123); This second solution is much better because not only the code is simpler but more importantly there is less space requirement without the intermediate calculations. However, the composition f123 must be determined at compile time and thus is fixed at run time. How would I try to do this efficiently if the composition is to be determined at run time? For example, if this code was in a RPC service and the actual composition--which can be any permutation of f1, f2, and f3--is based on arguments from the RPC call.

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• How to render all records from a nested set into a real html tree

  - by Christoph Schiessl

  I'm using the awesome_nested_set plugin in my Rails project. I have two models that look like this (simplified): class Customer < ActiveRecord::Base has_many :categories end class Category < ActiveRecord::Base belongs_to :customer # Columns in the categories table: lft, rgt and parent_id acts_as_nested_set :scope => :customer_id validates_presence_of :name # Further validations... end The tree in the database is constructed as expected. All the values of parent_id, lft and rgt are correct. The tree has multiple root nodes (which is of course allowed in awesome_nested_set). Now, I want to render all categories of a given customer in a correctly sorted tree like structure: for example nested <ul> tags. This wouldn't be too difficult but I need it to be efficient (the less sql queries the better). Update: Figured out that it is possible to calculate the number of children for any given Node in the tree without further SQL queries: number_of_children = (node.rgt - node.lft - 1)/2. This doesn't solve the problem but it may prove to be helpful.

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• When is a bool not a bool (compiler warning C4800)

  - by omatai

  Consider this being compiled in MS Visual Studio 2005 (and probably others): CPoint point1( 1, 2 ); CPoint point2( 3, 4 ); const bool point1And2Identical( point1 == point2 ); // C4800 warning const bool point1And2TheSame( ( point1 == point2 ) == TRUE ); // no warning What the...? Is the MSVC compiler brain-dead? As far as I can tell, TRUE is #defined as 1, without any type information. So by what magic is there any difference between these two lines? Surely the type of the expression inside the brackets is the same in both cases? [This part of the question now satisfactorily answered in the comments just below] Personally, I think that avoiding the warning by using the == TRUE option is ugly (though less ugly than the != 0 alternative, despite being more strictly correct), and it is better to use #pragma warning( disable:4800 ) to imply "my code is good, the compiler is an ass". Agree? Note - I have seen all manner of discussion on C4800 talking about assigning ints to bools, or casting a burger combo with large fries (hold the onions) to a bool, and wondering why there are strange results. I can't find a clear answer on what seems like a much simpler question... that might just shine line on C4800 in general.

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• Is there a proper and wrong way to format CSS?

  - by DavidR

  When I first started writing CSS, I was writing it in an expanded form div.class { margin: 10px 5px 3px; border: 1px solid #333; font-weight: bold; } .class .subclass { text-align:right; } but now I find myself writing css like this: (Example from code I'm actually writing now) .object1 {} .scrollButton{width:44px;height:135px;} .scrollButton img {padding:51px 0 0 23px;} .object2 {width:165px;height:94px;margin:15px 0 0 23px;padding:15px 0 0 10px;background:#fff;} .featuredObject .symbol{line-height:30px; padding-top:6px;} .featuredObject .value {width:90px;} .featuredObject .valueChange {padding:5px 0 0 0;} .featuredObject img {position:absolute;margin:32px 0 0 107px;} and I'm beginning to worry because a lot of the time I see the first form done in examples online, while I find the second form a lot easier for me to work with. It has a lower vertical height, so I can see all the classes at a glance with less scrolling, the tabulation of the hierarchy seems more apparent, and it looks more like code I'd write with javascript or html. Is this a valid way of doing code, or to keep with standards when putting it online should I use the vertical form instead?

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• Can a T-SQL variable represent an entire row?

  - by elbillaf

  I'm coding for MS SQL Server 10. I have two databases that contain dozens of tables. Each table in one database contains a table with the same name in the other database. Tables with the same name have identical format (fields and data types). The contents of the two tables are similar but not identical. I need to update one based on changes made to the other, but only under certain circumstances. I think I want to use a cursor for this, but I can't find a good example to go by. So far, the MSDN examples are reading one field at a time into a variable. I do need to be able to read /modify two fields which are identical in each table, but I gotta believe there's something less tedious than declaring variables for every field of every table. I would like to be able to FETCH an entire row, check a couple of fields and then make a decision of whether I want to write the entire row to the other table after changing two fields - but do I have to declare variables for EVERY field I want to fetch / write? There's no way to just FETCH an entire row and write an entire row?

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• Quickly accessing files in a 'project'

  - by bbbscarter

  Hi all. I'm looking for a way to quickly open files in my project's source tree. What I've been doing so far is adding files to the file-name-cache like so: (file-cache-add-directory-recursively (concat project-root "some/sub/folder") ".*\\.\\(py\\)$") after which I can use anything-for-files to access any file in the source tree with about 4 keystrokes. Unfortunately, this solution started falling over today. I've added another folder to the cache and emacs has started running out of memory. What's weird is that this folder contains less than 25% of files I'm adding, and yet emacs memory use goes up from 20mb to 400mb on adding just this folder. The total number of files is around 2000, so this memory use seems very high. Presumably I'm abusing the file cache. Anyway, what do other people do for this? I like this solution for its simplicity and speed; I've looked at some of the many, many project management packages for emacs and none of them really grabbed me... Thanks in advance! Simon

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