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  • Get most left|right|top|bottom point contained in box

    - by skyman
    I'm storing Points Of Interest (POI) in PostgreSQL database, and retrieve them via PHP script to Android application. To reduce internet usage I want my mobile app to know if there are any points in the neighborhood of currently displayed area. My idea is to store bounds of the rectangle containing all points already retrieved (in other words: nearest point on the left (West) of most west already retrieved, nearest point above (North) of most north already retrieved etc.) and I will make next query when any edge of screen goes outside of this bounds. Currently I can retrieve points which are in "single screen" (in the area covered by currently displayed map) using: SELECT * FROM ch WHERE loc <@ (box '((".-$latSpan.", ".$lonSpan."),(".$latSpan.", ".-$lonSpan."))' + point '".$loc."') Now I need to know four most remote points in each direction, than I will be able to retrieve next four "more remote" points. Is there any possibility to get those points (or box) directly from PostgreSQL (maybe using some "aggregate points to box" function)?

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  • Fitting Gaussian KDE in numpy/scipy in Python

    - by user248237
    I am fitting a Gaussian kernel density estimator to a variable that is the difference of two vectors, called "diff", as follows: gaussian_kde_covfact(diff, smoothing_param) -- where gaussian_kde_covfact is defined as: class gaussian_kde_covfact(stats.gaussian_kde): def __init__(self, dataset, covfact = 'scotts'): self.covfact = covfact scipy.stats.gaussian_kde.__init__(self, dataset) def _compute_covariance_(self): '''not used''' self.inv_cov = np.linalg.inv(self.covariance) self._norm_factor = sqrt(np.linalg.det(2*np.pi*self.covariance)) * self.n def covariance_factor(self): if self.covfact in ['sc', 'scotts']: return self.scotts_factor() if self.covfact in ['si', 'silverman']: return self.silverman_factor() elif self.covfact: return float(self.covfact) else: raise ValueError, \ 'covariance factor has to be scotts, silverman or a number' def reset_covfact(self, covfact): self.covfact = covfact self.covariance_factor() self._compute_covariance() This works, but there is an edge case where the diff is a vector of all 0s. In that case, I get the error: File "/srv/pkg/python/python-packages/python26/scipy/scipy-0.7.1/lib/python2.6/site-packages/scipy/stats/kde.py", line 334, in _compute_covariance self.inv_cov = linalg.inv(self.covariance) File "/srv/pkg/python/python-packages/python26/scipy/scipy-0.7.1/lib/python2.6/site-packages/scipy/linalg/basic.py", line 382, in inv if info>0: raise LinAlgError, "singular matrix" numpy.linalg.linalg.LinAlgError: singular matrix What's a way to get around this? In this case, I'd like it to return a density that's essentially peaked completely at a difference of 0, with no mass everywhere else. thanks.

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  • Why does division yield a vastly different result than multiplication by a fraction in floating points.

    - by Avram
    I understand why floating point numbers can't be compared, and know about the mantissa and exponent binary representation, but I'm no expert and today I came across something I don't get: Namely lets say you have something like: float denominator, numerator, resultone, resulttwo; resultone = numerator / denominator; float buff = 1 / denominator; resulttwo = numerator * buff; To my knowledge different flops can yield different results and this is not unusual. But in some edge cases these two results seem to be vastly different. To be more specific in my GLSL code calculating the Beckmann facet slope distribution for the Cook-Torrance lighitng model: float a = 1 / (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); float b = clampedCosHalfNormal * clampedCosHalfNormal - 1.0; float c = facetSlopeRMS * facetSlopeRMS * clampedCosHalfNormal * clampedCosHalfNormal; facetSlopeDistribution = a * exp(b/c); yields very very different results to float a = (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); facetDlopeDistribution = exp(b/c) / a; Why does it? The second form of the expression is problematic. If I say try to add the second form of the expression to a color I get blacks, even though the expression should always evaluate to a positive number. Am I getting an infinity? A NaN? if so why?

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  • Subview of custom NSView is resizing itself to fit within its superview

    - by Jonathan Patt
    I have a custom NSView which contains a subview—for the purposes of solving this issue, the top level view is simply acting as a container and automatically resizes to fit within the window. Its subview draws a rectangle 10 pixels inset from the edge of the window, except for the bottom, which should get clipped by the window until it's resized to show the entire rectangle. It does not, however, behave as I intend, and instead shrinks the height of the rectangle when its superview has a smaller height than it does. How do I avoid this and have it stay at its proper height and instead get clipped when the superview is smaller? The parent view's implementation code is: - (id)initWithFrame:(NSRect)frameRect { self = [super initWithFrame:frameRect]; if (self) { subView = [[SubView alloc] initWithFrame:frameRect]; } return self; } - (void)drawRect:(NSRect)dirtyRect { [[NSColor grayColor] set]; [subView setFrame:NSMakeRect(10, 10, dirtyRect.size.width - 20, 500)]; [self addSubview:subView]; } - (BOOL)isFlipped { return YES; } And the subview is just: - (void)drawRect:(NSRect)dirtyRect { [[NSColor blackColor] set]; [NSBezierPath strokeRect:dirtyRect]; } - (BOOL)isFlipped { return YES; }

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  • 3x3 Sobel operator and gradient features

    - by pithyless
    Reading a paper, I'm having difficulty understanding the algorithm described: Given a black and white digital image of a handwriting sample, cut out a single character to analyze. Since this can be any size, the algorithm needs to take this into account (if it will be easier, we can assume the size is 2^n x 2^m). Now, the description states given this image we will convert it to a 512-bit feature (a 512-bit hash) as follows: (192 bits) computes the gradient of the image by convolving it with a 3x3 Sobel operator. The direction of the gradient at every edge is quantized to 12 directions. (192 bits) The structural feature generator takes the gradient map and looks in a neighborhood for certain combinations of gradient values. (used to compute 8 distinct features that represent lines and corners in the image) (128 bits) Concavity generator uses an 8-point star operator to find coarse concavities in 4 directions, holes, and lagrge-scale strokes. The image feature maps are normalized with a 4x4 grid. I'm for now struggling with how to take an arbitrary image, split into 16 sections, and using a 3x3 Sobel operator to come up with 12 bits for each section. (But if you have some insight into the other parts, feel free to comment :)

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  • Using YQL multi-query & XPath to parse HTML, how to escape nested quotes?

    - by Tivac
    The title is more complicated than it has to be, here's the problem query. SELECT * FROM query.multi WHERE queries=" SELECT * FROM html WHERE url='http://www.stumbleupon.com/url/http://www.guildwars2.com' AND xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span'; SELECT * FROM xml WHERE url='http://services.digg.com/1.0/endpoint?method=story.getAll&link=http://www.guildwars2.com'; SELECT * FROM json WHERE url='http://api.tweetmeme.com/url_info.json?url=http://www.guildwars2.com'; SELECT * FROM xml WHERE url='http://api.facebook.com/restserver.php?method=links.getStats&urls=http://www.guildwars2.com'; SELECT * FROM json WHERE url='http://www.reddit.com/button_info.json?url=http://www.guildwars2.com'" Specifically this line, xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span' It's problematic because of the quoting, I have to nest them three levels deep and I've run out of quote characters to use. I've tried the following variations without success: //no attribute quoting xpath='//li[@class=listLi]/div[@class=views]/a/span' //try to quote attribute w/ backslash & single quote xpath='//li[@class=\'listLi\']/div[@class=\'views\']/a/span' //try to quote attribute w/ backslash & double quote xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span' //try to quote attribute with double single quotes, like SQL xpath='//li[@class=''listLi'']/div[@class=''views'']/a/span' //try to quote attribute with double double quotes, like SQL xpath='//li[@class=""listLi""]/div[@class=""views""]/a/span' //try to quote attribute with quote entities xpath='//li[@class=&quot;listLi&quot;]/div[@class=&quot;views&quot;]/a/span' //try to surround XPath with backslash & double quote xpath=\"//li[@class='listLi']/div[@class='views']/a/span\" //try to surround XPath with double double quote xpath=""//li[@class='listLi']/div[@class='views']/a/span"" All without success. I don't see much out there about escaping XPath strings but everything I've found seems to be variations on using concat (which won't help because neither ' nor " are available) or html entities. Not using quotes for the attributes doesn't throw an error but fails because it's not the actual XPath string I need. I don't see anything in the YQL docs about how to handle escaping. I'm aware of how edge-casey this is but was hoping they'd have some sort of escaping guide.

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  • QT- QImage and multi-threading problem.

    - by umanga
    Greetings all, Please refer to image at : http://i48.tinypic.com/316qb78.jpg We are developing an application to extract cell edges from MRC images from electron microscope. MRC file format stores volumetric pixel data (http://en.wikipedia.org/wiki/Voxel) and we simply use 3D char array(char***) to load and store data (gray scale values) from a MRC file. As shown in the image,there are 3 viewers to display XY,YZ and ZX planes respectively. Scrollbars on the top of the viewers use to change the image slice along an axis. Here is the steps we do when user changes the scrollbar position. 1) get the new scrollbar value.(this is the selected slice) 2) for the relavant plane (YZ,XY or ZX), generate (char* slice;) array for the selected slice by reading 3D char array (char***) 3) Create a new QImage* (Format_RGB888) and set pixel values by reading 'slice' (using img-setPixel(x,y,c);) 4) This new QImage* is painted in the paintEvent() method. We are going to execute "edge-detection" process in a seperate thread since it is an intensive process.During this process we need to draw detected curve (set of pixels) on top of above QImage*.(as a layer).This means we need to call drawPoint() methods outside the QT thread. Is it the best wayto use QImage for this case? What is the best way to execute QT drawing methods from another thread? thanks in advance,

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  • Visual studio not detecting that exe is out of date after perforce revert

    - by CHaskell2
    This is a bit of an odd situation. Here's what's happening. So, we have a VS2008 project which outputs to a number of files under perforce control. These files have the always writable flag set. I compile the project in VS, which gives me up to date binaries on my machine. If I then revert those binaries via perforce, I have the version of the binaries that were up on perforce (ie, old ones.) Despite this, compiling the project again at this point detects no changes and will not remake those binaries. In a way, this makes sense, since none of the code or obj files have changed, but it's not really what I want to happen. This comes up in an edge case on our automated build server. I can think of tons of different little hacks I could do to fix this, but I'm thinking I could be missing something fundamental here. The actual build process uses the Unreal build tool, so there is a bit of magic going on behind the scenes that I'm not entirely familiar with too. Edit: This is a C/C++ project, forgot to mention that.

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  • Simple first-child js?

    - by Glister
    Searching for a simple first-child detection via javascript (no framework). It should add some class for the first child of the element. Like a css-hacks for ie, but in javascript and for a html file. Must work similar to :first-child When I say no framework, I mean some code like this: <script type="text/javascript">document.documentElement.id = "js"</script> For example: <div class="terms"> <dl> <dt>Term 1 name</dt> <dd>Term 1 description</dd> </dl> <dl> <dt>Term 2 name</dt> <dd>Term 2 description</dd> </dl> <dl> <dt>Term 3 name</dt> <dd>Term 3 description</dd> </dl> </div> Three <dl>, the first one includes Term 1. This css won't work in IE6, thats why I'm searching for a javascript solution. CSS-hacks are not allowed. .terms dl:first-child { float: right; }

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  • Django users and authentication from external source

    - by Boldewyn
    I have a Django app that gets it's data completely from an external source (queried via HTTP). That is, I don't have the option for a local database. Session data is stored in the cache (on my development server I use a SQLite database, so that is no error source). I'm using bleeding edge Django 1.1svn. Enter the problem: I want to use Django's own authentication system for the users. It seems quite simple to write my own Authentication Backend, but always just under the condition that you have a local database where to save the users. Without database my main problem is persistence. I tried it with the following (assume that datasource.get() is a function that returns some kind of dict): class ModelBackend (object): """Login backend.""" def authenticate (self, username=None, password=None): """Check, if a given user/password combination is valid""" data = datasource.get ('login', username, password) if data and data['ok']: return MyUser (username=username) else: raise TypeError return None def get_user (self, username): """get data about a specific user""" try: data = datasource.get ('userdata', username) if data and data['ok']: return data.user except: pass return None class MyUser (User): """Django user who isn't saved in DB""" def save (self): return None But the intentionally missing save() method on MyUser seems to break the session storage of a login. How should MyUser look like without a local database?

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  • Is this a good approach to address double-base64-encoding?

    - by Freiheit
    My software understands attachments, like PNGs attached to user records. These attachments are usually sent in from outside sources as a Base64 encoded string. The database stores whatever data it is given, Base64 encoded or not. When I serve up the attachment for download I do this: if (Base64.isBase64(data)) { data = Base64.decodeBase64(data); } There is a potential for data that is double encoded. For instance the sender of a message had base64 encoded data, then encoded it again when building the message to send to me. I think the following code would address that circumstance: while (Base64.isBase64(data)) { data = Base64.decodeBase64(data); } So if data is encoded multiple times, it would be decoded until its in its 'raw' state and then served up for download. Is this approach an acceptable way to address that problem? Ideally some sort of checking could happen at the edge when I receive attachment data, but that will take more time. This looping seems to be a faster way to do it. The 'Base64' library is Apache Commons: http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html I trust it to properly identify Base64 encoded data.

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  • Parameterized Queries /Without/ using queries.

    - by Aren B
    I've got a bit of a poor situation here. I'm stuck working with commerce server, which doesn't do a whole lot of sanitization/parameterization. I'm trying to build up my queries to prevent SQL Injection, however some things like the searches / where clause on the search object need to be built up, and there's no parameterized interface. Basically, I cannot parameterize, however I was hoping to be able to use the same engine to BUILD my query text if possible. Is there a way to do this, aside from writing my own parameterizing engine which will probably still not be as good as parameterized queries? Update: Example The where clause has to be built up as a sql query where clause essentially: CatalogSearch search = /// Create Search object from commerce server search.WhereClause = string.Format("[cy_list_price] > {0} AND [Hide] is not NULL AND [DateOfIntroduction] BETWEEN '{1}' AND '{2}'", 12.99m, DateTime.Now.AddDays(-2), DateTime.Now); *Above Example is how you refine the search, however we've done some testing, this string is NOT SANITIZED. This is where my problem lies, because any of those inputs in the .Format could be user input, and while i can clean up my input from text-boxes easily, I'm going to miss edge cases, it's just the nature of things. I do not have the option here to use a parameterized query because Commerce Server has some insane backwards logic in how it handles the extensible set of fields (schema) & the free-text search words are pre-compiled somewhere. This means I cannot go directly to the sql tables What i'd /love/ to see is something along the lines of: SqlCommand cmd = new SqlCommand("[cy_list_price] > @MinPrice AND [DateOfIntroduction] BETWEEN @StartDate AND @EndDate"); cmd.Parameters.AddWithValue("@MinPrice", 12.99m); cmd.Parameters.AddWithValue("@StartDate", DateTime.Now.AddDays(-2)); cmd.Parameters.AddWithValue("@EndDate", DateTime.Now); CatalogSearch search = /// constructor search.WhereClause = cmd.ToSqlString();

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  • H.264 / FLV best practices for HTML

    - by Steve Murch
    I run a website with about 700 videos (And no, it's not porn -- get your mind out of the gutter :-) ). The videos are currently in FLV format. We use the JWPlayer to render those videos. IIS6 hosted. Everything works just fine. As I understand it, H.264 (not FLV and likely not OGG) is the emerging preferred HTML5 video standard. Today, the iPad really only respects H.264 or YouTube. Presumably, soon many more important browsers will follow Apple's lead and respect only the HTML5 tag. OK, so I think I can figure out how to convert my existing videos into the proper H.264 format. There are various tools available, including ffmpeg.exe. I haven't tried it yet, but I don't think that's going to be a problem after fiddling with the codec settings. My question is more about the container itself -- that is, planning graceful transition for all users. What's the best-practice recommendation for rendering these videos? If I just use the HTML5 tag, then presumably any browser that doesn't yet support HTML5 won't see the videos. And if I render them in Flash format via the JWPlayer or some other player, then they won't be playable on the iPad. Do I have to do ugly UserAgent detection here to figure out what to render? I know the JWPlayer supports H.264 media, but isn't the player itself a Flash component and therefore not playable on the iPad? Sorry if I'm not being clear, but I'm scratching my head on a graceful transition plan that will work for current browsers, the iPad and the upcoming HTML5 wave. I'm not a video expert, so any advice would be most welcome, thanks.

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  • How can I improve my real-time behavior in multi-threaded app using pthreads and condition variables

    - by WilliamKF
    I have a multi-threaded application that is using pthreads. I have a mutex() lock and condition variables(). There are two threads, one thread is producing data for the second thread, a worker, which is trying to process the produced data in a real time fashion such that one chuck is processed as close to the elapsing of a fixed time period as possible. This works pretty well, however, occasionally when the producer thread releases the condition upon which the worker is waiting, a delay of up to almost a whole second is seen before the worker thread gets control and executes again. I know this because right before the producer releases the condition upon which the worker is waiting, it does a chuck of processing for the worker if it is time to process another chuck, then immediately upon receiving the condition in the worker thread, it also does a chuck of processing if it is time to process another chuck. In this later case, I am seeing that I am late processing the chuck many times. I'd like to eliminate this lost efficiency and do what I can to keep the chucks ticking away as close to possible to the desired frequency. Is there anything I can do to reduce the delay between the release condition from the producer and the detection that that condition is released such that the worker resumes processing? For example, would it help for the producer to call something to force itself to be context switched out? Bottom line is the worker has to wait each time it asks the producer to create work for itself so that the producer can muck with the worker's data structures before telling the worker it is ready to run in parallel again. This period of exclusive access by the producer is meant to be short, but during this period, I am also checking for real-time work to be done by the producer on behalf of the worker while the producer has exclusive access. Somehow my hand off back to running in parallel again results in significant delay occasionally that I would like to avoid. Please suggest how this might be best accomplished.

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  • Problem with UIScrollView

    - by leon
    Hi, Sorry for long winded post. I am trying to understand UIScrollView and running into very simple problem. I am creating a scroll view I am making this view 1.5 size larger then normal size Using UIScrollView I expect to see some edge elements of view out of bounds, but should be able to pan the view therefore bringing missing elements back to the visible area. However I am seeing that I can't just pan/scroll view anyway I want, instead view always wants to scroll up, as soon as move away my finger from the screen (touch end event). I am not handling any touches, etc - I just want to understand why does not scaled view stay put where I scroll it? CGRect viewFrame = self.view.frame ; viewFrame.size.width *= 1.5; viewFrame.size.height *= 1.5; CGSize mySize = viewFrame.size; [ ((UIScrollView *) self.view) setContentSize: mySize]; self.view.transform = CGAffineTransformMakeScale(1.5, 1.5); What I really trying to accomplish is something similar to Number on iPad (the same code will work on iPhone): There is a view with lots of controls on it (order entry form) User can zoom into the entire form so all elements look bigger user can pan the form therefore bringing various elements into the visible area of the screen. It seems that UIScrollView can should be able to handle zoom and pan actions (for now I am using Affine Transform to zoom in to the order entry form and iPad) Thanks

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  • Trying to use a authlogic-connect as a plugin in place of gem - Server doesn't start

    - by Arkid
    I am trying to use Authlogic-connect as a plugin in Rails 3 in place of a gem. I have made an entry in the gemfile as gem "authlogic-connect", :require => "authlogic-connect", :path => "localgems" Now when I run the bundle install, it runs fine. When I try to start the server i get the error Could not find gem 'authlogic-connect (>= 0, runtime)' in source at localgems. Source does not contain any versions of 'authlogic-connect (>= 0, runtime)' Try running `bundle install`. I have placed the unzipped Gem renamed as authlogic-connect in the localgems folder. what is the problem? Here is what I get on using rails plugin install arkidmitra$ rails plugin install git://github.com/viatropos/authlogic-connect.git Usage: rails new APP_PATH [options] Options: [--skip-gemfile] # Don't create a Gemfile -d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db) # Default: sqlite3 -O, [--skip-active-record] # Skip Active Record files [--dev] # Setup the application with Gemfile pointing to your Rails checkout -J, [--skip-prototype] # Skip Prototype files -T, [--skip-test-unit] # Skip Test::Unit files -G, [--skip-git] # Skip Git ignores and keeps -r, [--ruby=PATH] # Path to the Ruby binary of your choice # Default: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL) -b, [--builder=BUILDER] # Path to an application builder (can be a filesystem path or URL) [--edge] # Setup the application with Gemfile pointing to Rails repository Runtime options: -q, [--quiet] # Supress status output -s, [--skip] # Skip files that already exist -f, [--force] # Overwrite files that already exist -p, [--pretend] # Run but do not make any changes Rails options: -h, [--help] # Show this help message and quit -v, [--version] # Show Rails version number and quit Description: The 'rails new' command creates a new Rails application with a default directory structure and configuration at the path you specify. Example: rails new ~/Code/Ruby/weblog This generates a skeletal Rails installation in ~/Code/Ruby/weblog. See the README in the newly created application to get going.

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  • Formula parsing / evaluation routine or library with generic DLookup functionality

    - by tbone
    I am writing a .Net application where I must support user-defined formulas that can perform basic mathematics, as well as accessing data from any arbitrary table in the database. I have the math part working, using JScript Eval(). What I haven't decided on is what a nice way is to do the generic table lookups. For example, I may have a formula something like: Column: BonusAmount Formula: {CurrentSalary} * 1.5 * {[SystemSettings][Value][SettingName=CorpBonus AND Year={Year}]} So, in this example I would replace {xxx} and {Year} with the value of Column xxx from the current table, and I would replace the second part with the value of (select Value from SystemSettings WHERE SettingName='CorpBonus' AND Year=2008) So, basically, I am looking for something very much like the MS Access DLookup function: DLookup ( expression, domain, [criteria] ) DLookup("[UnitPrice]", "Order Details", "OrderID = 10248") But, I also need to overall parsing routine that can tell whether to just look up in the current row, or to look into another table. Would also be nice to support aggregate functions (ie: DAvg, DMax, etc), as well as all the weird edge cases handled. So I wonder if anyone knows of any sort of an existing library, or has a nice routine that can handle this formula parsing and database lookup / aggregate function resolution requirements.

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  • Should a Perl constructor return an undef or a "invalid" object?

    - by DVK
    Question: What is considered to be "Best practice" - and why - of handling errors in a constructor?. "Best Practice" can be a quote from Schwartz, or 50% of CPAN modules use it, etc...; but I'm happy with well reasoned opinion from anyone even if it explains why the common best practice is not really the best approach. As far as my own view of the topic (informed by software development in Perl for many years), I have seen three main approaches to error handling in a perl module (listed from best to worst in my opinion): Construct an object, set an invalid flag (usually "is_valid" method). Often coupled with setting error message via your class's error handling. Pros: Allows for standard (compared to other method calls) error handling as it allows to use $obj->errors() type calls after a bad constructor just like after any other method call. Allows for additional info to be passed (e.g. 1 error, warnings, etc...) Allows for lightweight "redo"/"fixme" functionality, In other words, if the object that is constructed is very heavy, with many complex attributes that are 100% always OK, and the only reason it is not valid is because someone entered an incorrect date, you can simply do "$obj->setDate()" instead of the overhead of re-executing entire constructor again. This pattern is not always needed, but can be enormously useful in the right design. Cons: None that I'm aware of. Return "undef". Cons: Can not achieve any of the Pros of the first solution (per-object error messages outside of global variables and lightweight "fixme" capability for heavy objects). Die inside the constructor. Outside of some very narrow edge cases, I personally consider this an awful choice for too many reasons to list on the margins of this question. UPDATE: Just to be clear, I consider the (otherwise very worthy and a great design) solution of having very simple constructor that can't fail at all and a heavy initializer method where all the error checking occurs to be merely a subset of either case #1 (if initializer sets error flags) or case #3 (if initializer dies) for the purposes of this question. Obviously, choosing such a design, you automatically reject option #2.

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  • vestal_versions : problem with column named changes

    - by arkannia
    Hi, I am working with vestal version for 2 months. Everything was fine until this afternoon. I didn't done anything special(or i don't remembered...) but the code works fine on others computers... The problem is that i'm not able to save my model anymore: rails give me this error : ActiveRecord::DangerousAttributeError: changes is defined by ActiveRecord changes field is by default an activerecord method. With the console, the message is the next : ActiveRecord::DangerousAttributeError: changes is defined by ActiveRecord Here are my local gem files: abstract (1.0.0) actionmailer (3.0.0.beta3) actionpack (3.0.0.beta3) activemodel (3.0.0.beta3) activerecord (3.0.0.beta3) activeresource (3.0.0.beta3) activesupport (3.0.0.beta3) arel (0.3.3) builder (2.1.2) bundler (0.9.25, 0.9.24) crack (0.1.7) erubis (2.6.5) god (0.9.0) haml (3.0.1, 2.2.23) i18n (0.3.7) mail (2.2.0) memcache-client (1.8.3) memcached (0.17.7) mime-types (1.16) polyglot (0.3.1) rack (1.1.0) rack-mount (0.6.3) rack-test (0.5.3) rails (3.0.0.beta3) railties (3.0.0.beta3) rake (0.8.7) savon (0.7.8, 0.7.6) text-format (1.0.0) text-hyphen (1.0.0) thor (0.13.6, 0.13.4) treetop (1.4.5) tzinfo (0.3.20) And here my Gemfile source 'http://gemcutter.org' gem "rails", "3.0.0.beta3" gem "will_paginate", "3.0.pre" #gem 'nokogiri' #gem 'curb' #gem 'handsoap' gem 'savon' gem 'mysql' gem 'haml', '2.2.23' #gem 'haml', '3.0.1' gem 'hpricot' gem 'i18n', '> 0.3.5' gem 'i18n_routing' gem 'i18n_auto_scoping' gem 'handler301', :git => 'http://github.com/kwi/handler301.git' gem 'seo_meta_builder' gem 'vestal_versions' #gem 'paperclip', :git => 'git://github.com/thoughtbot/paperclip.git', :branch => 'rails3' ## Bundle edge rails: gem "rails", :git => "git://github.com/rails/rails.git" ## Bundle the gems you use: # gem "bj" # gem "hpricot", "0.6" # gem "sqlite3-ruby", :require => "sqlite3" # gem "aws-s3", :require => "aws/s3" ## Bundle gems used only in certain environments: # gem "rspec", :group => :test # group :test do # gem "webrat" # end If you have any suggestions to solve this issue, i'll be glad to hear them ! Thanks

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  • detecting pauses in a spoken word audio file using pymad, pcm, vad, etc

    - by james
    First I am going to broadly state what I'm trying to do and ask for advice. Then I will explain my current approach and ask for answers to my current problems. Problem I have an MP3 file of a person speaking. I'd like to split it up into segments roughly corresponding to a sentence or phrase. (I'd do it manually, but we are talking hours of data.) If you have advice on how to do this programatically or for some existing utilities, I'd love to hear it. (I'm aware of voice activity detection and I've looked into it a bit, but I didn't see any freely available utilities.) Current Approach I thought the simplest thing would be to scan the MP3 at certain intervals and identify places where the average volume was below some threshold. Then I would use some existing utility to cut up the mp3 at those locations. I've been playing around with pymad and I believe that I've successfully extracted the PCM (pulse code modulation) data for each frame of the mp3. Now I am stuck because I can't really seem to wrap my head around how the PCM data translates to relative volume. I'm also aware of other complicating factors like multiple channels, big endian vs little, etc. Advice on how to map a group of pcm samples to relative volume would be key. Thanks!

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  • How do you create a non-Thread-based Guice custom Scope?

    - by Russ
    It seems that all Guice's out-of-the-box Scope implementations are inherently Thread-based (or ignore Threads entirely): Scopes.SINGLETON and Scopes.NO_SCOPE ignore Threads and are the edge cases: global scope and no scope. ServletScopes.REQUEST and ServletScopes.SESSION ultimately depend on retrieving scoped objects from a ThreadLocal<Context>. The retrieved Context holds a reference to the HttpServletRequest that holds a reference to the scoped objects stored as named attributes (where name is derived from com.google.inject.Key). Class SimpleScope from the custom scope Guice wiki also provides a per-Thread implementation using a ThreadLocal<Map<Key<?>, Object>> member variable. With that preamble, my question is this: how does one go about creating a non-Thread-based Scope? It seems that something that I can use to look up a Map<Key<?>, Object> is missing, as the only things passed in to Scope.scope() are a Key<T> and a Provider<T>. Thanks in advance for your time.

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  • Java Playing Cards Game Framework

    - by isme
    My friends and I at uni love playing Shithead into the wee hours. But soon we graduate and will leave town, so probably won't get together for a game for a while. I want to develop a Java app we can use to play Shithead and our other favorites over a network. An app like this already exists, but is ugly, buggy and does not support our house rules. The source is available, but is such a mess that I would really rather start from scratch than try to refactor it! Building my game using some standard playing card api or framework, if such a thing exists, would be better than starting from scratch. The answer to a similar SO question was to use the JPC-API, which allegedly provides basic playing card services and rendering. But this Sourceforge project currently makes available no files or source code! Is there an alternative, or somewhere else to find this framework? Soon I will need help with the following as well: Lobby services (finding other players) Gaming network protocol (to communicate moves between players) Gaming theory (to write the computer opponent) Winning condition detection Game UI development

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  • Video-codec rater by image comparison algorithm?

    - by Andreas Hornig
    Hi, perhaps anyone knows if this is possible. comparing image quality is almost imposible to describe without subjective influences. When someone rates an image quality as good there is at least one person, that doesn't think so. human preferences are always different. So, I would like to know if there is away to "rate" the image quality by an algorithm that compares the original image to the produced one in following issues colour change(difference pixel by pixel blur rate artifacts and macroblocking the first one would be the easiest one because you could check just the diffeence in colours and can give 3 values in +- of each hex-value both last once I don't know if this is possible, but the blocking could be detected by edge-finding. and the king's quest would be to do that for more then just one image, because video is done with several frames. perhaps you expert programmers could tell me, if such an automated algo can be done to bring some objective measurement divice into rating image quality. this could perhaps calm down some h.264 is better than x264 and better than vp8 and blaaah people :) Andreas 1st posted here http://www.hdtvtotal.com/index.php?name=PNphpBB2&file=viewtopic&p=9705

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  • Fixed mouse pointer with jQuery draggable

    - by MikeWyatt
    I'm building a little game in HTML5. The canvas element is a viewport into the game world. The user can move the viewport's position in the world by clicking and dragging with the mouse on a small icon. The problem is that the scrolling stops when the mouse pointer hits the edge of the screen. In all likelihood, that will limit scrolling in one of the directions severely, since the icon will be in one of the corners of the page. The only technical solution I can think of would be to somehow fix the mouse pointer's position on the icon and detect the relative movement each frame. Basically I would just reset the pointer position back to the center of the icon after each drag event. Unfortunately, I'm fairly positive that this is not possible. Playing with the user's pointer is a big no-no from a usability and security standpoint. So, is there any other way to do what I want? I'm primarily looking for technical ideas here, but suggestions for a more appropriate interface would also be welcome.

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  • Rails 3: Parsing XML

    - by gjb
    I have a simple XML document in the following format: <?xml version="1.0" encoding="utf-8"?> <object> <strField>Foo</strField> <intField>1</intField> <dateField>2010-11-03</dateField> <boolField>true</boolField> <nilField></nilField> </object> I would like to parse this into a Hash to be passed to Model.create: {:object => { :strField => 'Foo', :intField => 1, :dateField => Date.today, :boolField => true, :nilField => nil }} Sadly there are no "type" attributes in the XML, so using Hash.from_xml just parses each field as a string. What I am looking for is some sort of field type auto detection. I have also looked at Nokogiri, but that can't output as a Hash. What is the simplest and most efficient way to achieve this? Many thanks.

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