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• On-Demand thumbnail creation with django and nginx

  - by sharjeel

  I want to generate thumbnails of images on the fly. My site is built with django and deployed using nginx which serves all the static content and communicates with django/apache using reverse proxy. Right now, for every image in my site, I generate all required sizes of thumbnails on-hand and deliver them when required. The problem is that whenever I change the size of a thumbnail, I have to regenerate all of them (and they are tons). However now I'd like to generate the thumbnail the first time it is accessed and later on nginx would deliver the same file over n over. If I delete that thumbnail file because of lesser accesses, it should get generated automatically the next time. Thumbnails in my case also have watermarks which require some computation logic of my application so a webserver thumbnail module might not work very well. The size of the thumbnail can be embedded in the URL. So http://www.example.com/thumbnail/abc_320x240.jpg gets the 320x240 size of the thumbnail. The approach I'm looking right now is to let nginx lookup the file and if it doesn't exist, forward the query to my django application which would create the thumbnail and send either the response or a redirect string. However I'm not sure about the concurrency issues and any other issues which might pop up later. What is the appropriate way to achieve this?

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• Web-app currency input/manipulation/calculation with javascript .. there has got to be a better (fra

  - by dreftymac

  BACKGROUND: I am of the "user-input-lockdown" school of thought. Whenever possible, I try to mistrust and sanitize user input, both client side and server side; and I try to take multiple opportunities to restrict possible inputs to a known subset of possibilities, usually this means providing a lot of checkboxes and select lists. (This is from the usability side of things, I know security-wise that malicious users can easily bypass fixed user input GUI controls). PROBLEM: Anyway, the problem always arises with non-fixed input of currency. Whenever I have to accept a freely-specified dollar amount as user input, I always have to confront these problems/annoyances and it is always painful: 1) Make sure to give the user two input boxes for each currency_datapoint, one for the whole_dollar_part and another for the fractional_pennies_part 2) Whenever the user changes a currency_datapoint, provide keystroke-by-keystroke GUI feedback to let them know whether the currency_datapoint is well-formed, with context-appropriate validation rules (e.g., no negatives?, nonzero only?, numeric only!, no non-numeric punctuation! no symbols!) 3) For display purposes, every user-provided currency_datapoint should be translated to human-readable currency formatting (dollar sign, period, commas provided by the app, where appropriate) 4) For calculation purposes, every user-provided currency_datapoint has to be converted to integer (all pennies, to avoid floating point errors) and summed into a grand total with zero or more subtotals. 5) Every user-provided currency_datapoint should be displayed or displayable in a nice "tabular" format, which auto-updates as the user enters each currency_datapoint, including a baloon that warns when one or more currency_datapoints is not well-formed. I seem to be re-inventing this wheel every time I have to work with currency in Javascript on the client side (server side is a bit more flexible since most programming languages have higher-level currency formatting logic). QUESTION: Has anyone out there solved the problem of dealing with the above issues, client side, in a way that is server-side-technology-stack agnostic, (preferrably plain javascript or jquery)? This is getting old, there has to be a better way.

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• Create a strongly typed view which inherites a class which is concrete

  - by Ashwani K

  Hello All: I am having one class called BaseClass which contains some logic applicable to whole web site. In order to create a strongly typed view we need to inherit the page from System.Web.Mvc.ViewPage generic class. But In our case I have to Inherit the BaseClass from System.Web.Mvc.ViewPage to apply some common settings, but the BaseClass should be inherited from System.Web.Mvc.ViewPage< generic version. But I cannot inherit the BaseClass from System.Web.Mvc.ViewPage< as it will change other class also. So I created one more class of type BaseClass< inheriting it from System.Web.Mvc.ViewPage< and copied the whole code of BaseClass in BaseClass<. But the code in BaseClass is controlled by other team so it will be changed frequently so my BaseClass< should be in sync with BaseClass. Please help me in eliminating the code duplication or any other approach to make strongly typed View. Thanks Ashwani

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• Getting Started with Ruby & Ruby on Rails

  - by JakeTheSnake

  Some background: I'm a jack-of-all traits, one of which is programming. I learned VB6 through Excel and PHP for creating websites and so far it's worked out just fine for me. I'm not CS major or even mathematically inclined - logic is what interests me. Current status: I'm willing to learn new and more powerful languages; my first foray into such a route is learning Ruby. I went to the main Ruby website and did the interactive intro. (by the way, I'm currently getting redirected to google.com when I try the link...it's happening to other websites as well...is my computer infected?) I liked what I learned and wanted to get started using Ruby to create websites. I downloaded InstantRails and installed it; everything so far has been fine - the program starts up just fine, and I can test some Ruby code in the console. However my troubles begin when I try and view a web page with Ruby code present. Lastly, my problem: As in PHP, I can browse to the .php file directly and through using PHP tags and some simple 'echo' statements I can be on my way in making dynamic web pages. However with the InstantRails app working, accessing a .rb or .rhtml page doesn't produce similar results. I made a simple text file named 'test.rb' and put basic HTML tags in there (html, head, body) and the Ruby tags <%= and % with some ruby code inside. The web page actually shows the tags and the code - as if it's all just plain HTML. I take it Ruby isn't parsing the page before it is displayed to the user, but this is where my lack of understanding of the Ruby environment stops me short. Where do I go from here?

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• Sensible unit test possible?

  - by nkr1pt

  Could a sensible unit test be written for this code which extracts a rar archive by delegating it to a capable tool on the host system if one exists? I can write a test case based on the fact that my machine runs linux and the unrar tool is installed, but if another developer who runs windows would check out the code the test would fail, although there would be nothing wrong with the extractor code. I need to find a way to write a meaningful test which is not binded to the system and unrar tool installed. How would you tackle this? public class Extractor { private EventBus eventBus; private ExtractCommand[] linuxExtractCommands = new ExtractCommand[]{new LinuxUnrarCommand()}; private ExtractCommand[] windowsExtractCommands = new ExtractCommand[]{}; private ExtractCommand[] macExtractCommands = new ExtractCommand[]{}; @Inject public Extractor(EventBus eventBus) { this.eventBus = eventBus; } public boolean extract(DownloadCandidate downloadCandidate) { for (ExtractCommand command : getSystemSpecificExtractCommands()) { if (command.extract(downloadCandidate)) { eventBus.fireEvent(this, new ExtractCompletedEvent()); return true; } } eventBus.fireEvent(this, new ExtractFailedEvent()); return false; } private ExtractCommand[] getSystemSpecificExtractCommands() { String os = System.getProperty("os.name"); if (Pattern.compile("linux", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return linuxExtractCommands; } else if (Pattern.compile("windows", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return windowsExtractCommands; } else if (Pattern.compile("mac os x", Pattern.CASE_INSENSITIVE).matcher(os).find()) { return macExtractCommands; } return null; } }

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• Can you have multiple clipping regions in an HTML Canvas?

  - by emh

  I have code that loads a bunch of images into hidden img elements and then a Javascript loop which places each image onto the canvas. However, I want to clip each image so that it is a circle when placed on the canvas. My loop looks like this: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.beginPath(); context.arc(x+24, y+24, 20, 0, Math.PI * 2, 1); context.clip(); context.strokeStyle = "black"; context.drawImage(document.getElementById(avatar.id), x, y); context.stroke(); }); Problem is, only the first image is drawn (or is visible). If I remove the clipping logic: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.drawImage(document.getElementById(avatar.id), x, y); }); Then all my images are drawn. Is there a way to get each image individually clipped? I tried resetting the clipping area to be the entire canvas between images but that didn't work.

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• Perl Regex - Condensing groups of find/replace

  - by brydgesk

  I'm using Perl to perform some file cleansing, and am running into some performance issues. One of the major parts of my code involves standardizing name fields. I have several sections that look like this: sub substitute_titles { my ($inStr) = @_; ${$inStr} =~ s/ PHD./ PHD /; ${$inStr} =~ s/ P H D / PHD /; ${$inStr} =~ s/ PROF./ PROF /; ${$inStr} =~ s/ P R O F / PROF /; ${$inStr} =~ s/ DR./ DR /; ${$inStr} =~ s/ D.R./ DR /; ${$inStr} =~ s/ HON./ HON /; ${$inStr} =~ s/ H O N / HON /; ${$inStr} =~ s/ MR./ MR /; ${$inStr} =~ s/ MRS./ MRS /; ${$inStr} =~ s/ M R S / MRS /; ${$inStr} =~ s/ MS./ MS /; ${$inStr} =~ s/ MISS./ MISS /; } I'm passing by reference to try and get at least a little speed, but I fear that running so many (literally hundreds) of specific string replaces on tens of thousands (likely hundreds of thousands eventually) of records is going to hurt the performance. Is there a better way to implement this kind of logic than what I'm doing currently? Thanks Edit: Quick note, not all the replace functions are just removing periods and spaces. There are string deletions, soundex groups, etc.

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• get Random in ArrayList has error of java.lang.IllegalArgumentException: n must be positive

  - by gabrielle fregil

  In my ArrayList, i have get a random Item from my ArrayList for the equip method. Whenever i use my tester, the terminal window prints java.lang.IllegalArgumentException: n must be positive when I try to call random for the size. I tried to change the value of totalElements to the integer size of the elements, then the error would be an OutOfBoundsExeption import java.util.*; import java.util.Scanner; import java.util.Random; public class GameMaster { private int turn, totalElements; private boolean winner; private Avatar x1; private Avatar x2; private ArrayList<Item> inventory; public GameMaster(Avatar a1, Avatar a2) { x2 = a1; x1 = a2; turn = 1; winner = false; inventory = new ArrayList<Item>(); totalElements = 0; } private void fillInventory() { inventory.add( new Item( "Zealot Blades", true, 8 ) ); inventory.add( new Item( "BFG", true, 13 ) ); inventory.add( new Item( "Synthetic Cloth", false, 7 ) ); // more items inventory.add( new Item( "Gauss Rifle", true, 9 ) ); inventory.add( new Item( "Flight Unit", false, 6 ) ); totalElements = inventory.size(); } public String equip() { Avatar w; String a; if (turn%2==1) w=x2; else w=x1; if (w.beltIsFull()) { a = w.getName() + "'s belt is full. \n"; } else { turn++; Random generator = new Random(); Item rand = inventory.get(generator.nextInt(totalElements)); //terminal window in blueJ: java.lang.IllegalArgumentException: n must be positive a = w.getName()+" is equiped with "+rand.getName()+"."; } return a; }

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• SWT - Table Row - Changing font color

  - by jkteater

  Is it possible to change the font color for a row based on a value in one of the columns? My table has a column that displays a status. The value of the column is going to either be Failed or Success. If it is Success I would like for that rows font be green. If the status equals Failed, I want that rows font be red. Is this possible, if so where would I put the logic. EDIT Here is my Table Viewer code, I am not going to show all the columns, just a couple private void createColumns() { String[] titles = { "ItemId", "RevId", "PRL", "Dataset Name", "Printer/Profile" , "Success/Fail" }; int[] bounds = { 100, 75, 75, 150, 200, 100 }; TableViewerColumn col = createTableViewerColumn(titles[0], bounds[0], 0); col.setLabelProvider(new ColumnLabelProvider() { public String getText(Object element) { if(element instanceof AplotResultsDataModel.ResultsData) { return ((AplotResultsDataModel.ResultsData)element).getItemId(); } return super.getText(element); } }); col = createTableViewerColumn(titles[1], bounds[1], 1); col.setLabelProvider(new ColumnLabelProvider() { public String getText(Object element) { if(element instanceof AplotResultsDataModel.ResultsData) { return ((AplotResultsDataModel.ResultsData)element).getRevId(); } return super.getText(element); } }); --ETC

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• How to hide some nodes in Richfaces Tree (do not render nodes by condition)?

  - by VestniK

  I have a tree of categories and courses in my SEAM application. Courses may be active and inactive. I want to be able to show only active or all courses in my tree. I've decided to always build complete tree in my PAGE scope component since building this tree is quite expensive operation. I have boolean flag courseActive in the data wrapped by TreeNode<T>. Now I can't find the way to show courses node only if this flag is true. The best result I've achieved with the following code: <h:outputLabel for="showInactiveCheckbox" value="show all courses: "/> <h:selectBooleanCheckbox id="showInactiveCheckbox" value="#{categoryTreeEditorModel.showAllCoursesInTree}"> <a4j:support event="onchange" reRender="categoryTree"/> </h:selectBooleanCheckbox> <rich:tree id="categoryTree" value="#{categoryTree}" var="item" switchType="ajax" ajaxSubmitSelection="true" reRender="categoryTree,controls" adviseNodeOpened="#{categoryTreeActions.adviseRootOpened}" nodeSelectListener="#{categoryTreeActions.processSelection}" nodeFace="#{item.typeName}"> <rich:treeNode type="Category" icon="..." iconLeaf="..."> <h:outputText value="#{item.title}"/> </rich:treeNode> <rich:treeNode type="Course" icon="..." iconLeaf="..." rendered="#{item.courseActive or categoryTreeEditorModel.showAllCoursesInTree}"> <h:outputText rendered="#{item.courseActive}" value="#{item.title}"/> <h:outputText rendered="#{not item.courseActive}" value="#{item.title}" style="color:#{a4jSkin.inactiveTextColor}"/> </rich:treeNode> </rich:tree> the only problem is if some node is not listed in any rich:treeNode it just still shown with title obtained by Object.toString() method insted of being hidden. Does anybody know how to not show some nodes in the Richfases tree according to some condition?

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• Bring a subview to the top on mouseDown: AND keep receiving events (for dragging)

  - by d11wtq

  Ok, basically I have a view with a series of slightly overlapping subviews. When a subview is clicked, it moves to the top (among other things), by a really simple two-liner: -(void)mouseDown:(NSEvent *)theEvent { if (_selected) { // Don't do anything this subview is already in the foreground return; } NSView *superview = [self superview]; [self removeFromSuperview]; [superview addSubview:self position:NSWindowAbove relativeTo:nil]; } This works fine and seems to be the "normal" way to do this. The problem is that I'm now introducing some drag logic to the view, so I need to respond to -mouseDragged:. Unfortunately, since the view is removed from the view hierarchy and re-added in the process, I can have the view come to the foreground and be dragged in the same mouse action. It only drags if I leave go of the mouse and click on the view again, since the second click doesn't do any view hierarchy juggling. Is there anything I can do that will allow the view to move to the foreground like this, AND continue to receive the subsequent -mouseDragged: and -mouseUp: events that follow? I started along the lines of thinking of overriding -hitTest: in the superview and intercepting the mouseDown event in order to bring the view to the foreground before it actually receives the event. The problem here is, from within -hitTest:, how do I distinguish what type of event I'm actually performing the hit test for? I wouldn't want to move the subview to the foreground for other mouse events, such as mouseMoved etc.

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• Adding figures using contextual menu - Eclipse GEF

  - by darkie15

  All, I am creating a palette less eclipse plugin where am adding figures to the custom editor through the contextual menu, but am not finding a way to do it. Can anyone please guide me as to how to go about adding figures to editor dynamically through context menu i.e. adding actions/commands. Since Eclipse GEF plugin development finds so less examples to look at, I am adding my solution so others find it useful. This code helps to render a node to the editor. Source code for Action class to render figures to the editor: public class AddNodeAction extends EditorPartAction { public static final String ADD_NODE = "ADDNODE"; public AddNodeAction(IEditorPart editor) { super(editor); setText("Add a Node"); setId(ADD_NODE); // Important to set ID } public void run() { <ParentModelClass> parent= (<ParentModelClass>)getEditorPart().getAdapter(<ParentModelClass>.class); if (parent== null) return; CommandStack command = (CommandStack)getEditorPart().getAdapter(CommandStack.class); if (command != null) { CompoundCommand totalCmd = new CompoundCommand(); <ChildModelToRenderFigureCommand>cmd = new <ChildModelToRenderFigureCommand>(parent); cmd.setParent(parent); <ChildModelClass> newNode = new <ChildModelClass>(); cmd.setNode(newNode); cmd.setLocation(getLocation()); // Any location you wish to set to totalCmd.add(cmd); command.execute(totalCmd); } } @Override protected boolean calculateEnabled() { return true; } }

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• Unit testing opaque structure based C API

  - by Nicolas Goy

  I have a library I wrote with API based on opaque structures. Using opaque structures has a lot of benefits and I am very happy with it. Now that my API are stable in term of specifications, I'd like to write a complete battery of unit test to ensure a solid base before releasing it. My concern is simple, how do you unit test API based on opaque structures where the main goal is to hide the internal logic? For example, let's take a very simple object, an array with a very simple test: WSArray a = WSArrayCreate(); int foo = 5; WSArrayAppendValue(a, &foo); int *bar = WSArrayGetValueAtIndex(a, 0); if(&foo != bar) printf("Eroneous value returned\n"); else printf("Good value returned\n"); WSRelease(a); Of course, this tests some facts, like the array actually acts as wanted with 1 value, but when I write unit tests, at least in C, I usualy compare the memory footprint of my datastructures with a known state. In my example, I don't know if some internal state of the array is broken. How would you handle that? I'd really like to avoid adding codes in the implementation files only for unit testings, I really emphasis loose coupling of modules, and injecting unit tests into the implementation would seem rather invasive to me. My first thought was to include the implementation file into my unit test, linking my unit test statically to my library. For example: #include <WS/WS.h> #include <WS/Collection/Array.c> static void TestArray(void) { WSArray a = WSArrayCreate(); /* Structure members are available because we included Array.c */ printf("%d\n", a->count); } Is that a good idea? Of course, the unit tests won't benefit from encapsulation, but they are here to ensure it's actually working.

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• SIGABRT on any UIView touch

  - by bitcruncher

  Hi. I'm afraid no amount of Googling has been able to save my hyde on this. I seem to be getting SIGABRT error anytime I touch the screen of the phone, on any UIView. The debugger console posts this error before the SIGABRT: .... [310:207] *** -[UIView _exclusiveTouchView]: unrecognized selector sent to instance 0x14c0c0 .... [310:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIView _exclusiveTouchView]: unrecognized selector sent to instance 0x14c0c0' (this is not my specific call to _exclusiveTouchView, of course.) I would gladly post some code, but the truth is I cannot find (or guess) where this problem may be coming from. This is not happening on any ONE UIView but on all the UIViews in my stack. I can summarize the display logic, though, perhaps that will shed some light. So the application is created and a UIWindow is alloc'd. A single viewcontroller is then alloc'd, which makes and adds its own blank self.view, to which the other UIViews, representing the different game states, are attached. Interestingly enough, this error is does NOT happen on the Simulator, but happens consistently on the device. And I should also mention that the application has yet to override/use any of the touchesBegan:/Ended:/Moved: etc... In other words, this error happens without these methods in the code. I'm really not understanding where this error is coming from... Any suggestions?

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• Set fields with instrospection - Problem with String.valueOf(String)

  - by fabb

  Hey there! I'm setting public fields of the Object 'this' via reflection. Both the field name and the value are given as String. I use several various field types: Boolean, Integer, Float, Double, an own enum, and a String. It works with all of them except with a String. The exception that gets thrown is that no method with the Signature String.valueOf(String) exists... Now I use a dirty instanceof workaround to detect if each field is a String and in that case just copy the value to the field. private void setField(String field, String value) throws Exception { Field wField = this.getClass().getField(field); if(wField.get(this) instanceof String){ //TODO dirrrrty hack //stupid workaround as java.lang.String.valueOf(java.lang.String) fails... wField.set(this, value); }else{ Method parseMethod = wField.getType().getMethod("valueOf", new Class[]{String.class}); wField.set(this, parseMethod.invoke(wField, value)); } } Any ideas how to avoid that workaround? Do you think java.lang.String should support the method valueOf(String)? thanks, fabb

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• Break a while loop without using If or Break

  - by Justin

  I need to create a program that uses while to find the volume of a cylinder. I need the while loop to break if the user inputs a negative value for the height. My code looks like this: double sentinel=1, h=1, v=0, r, count=0; // declares all variables needed final double PI=3.14159; boolean NotNegative=true; while(NotNegative){// && count==0){ // while both the height is positive AND the total times run is 0 System.out.print("Enter height (Use negative to exit): "); // has the user input the height h=Double.parseDouble(br.readLine()); sentinel=h; // save sentinel as the inputted height while(sentinel>0){ System.out.print("Enter radius: "); // have the user input the radius r=Double.parseDouble(br.readLine()); v=PI*(r*r)*h; // find the volume System.out.println("The volume is " + v); // print out the volume count++; // increase the count each time this runs NotNegative=true; sentinel=-1; } } Any help?

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• Drupal Views api, add simple argument handler

  - by LanguaFlash

  Background: I have a complex search form that stores the query and it's hash in a cache. Once the cache is set, I redirect to something like /searchresults/e6c86fadc7e4b7a2d068932efc9cc358 where that big long string on the end is the md5 hash of my query. I need to make a new argument for views to know what the hash is good for. The reason for all this hastle is because my original search form is way to complex and has way to many arguments to consider putting them all into the path and expecting to do the filtering with the normal views arguments. Now for my question. I have been reading views 2 documentation but not figuring out how to accomplish this custom argument. It doesn't seem to me like this should be as hard as it seems to me like it must be. Leaving aside any knowledge of the veiws api, it would seem that all I need is a callback function that will take the argument from the path as it's only argument and return a list of node id's to filter to. Can anyone point me to a solution or give me some example code? Thanks for your help! You guys are great. PS. I am pretty sure that my design is the best I can come up with, lets don't get off my question and into cross checking my design logic if we can help it.

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• Can I delay the keyup event for jquery?

  - by Paul

  I'm using the rottentomatoes movie API in conjunction with twitter's typeahead plugin using bootstrap 2.0. I've been able to integerate the API but the issue I'm having is that after every keyup event the API gets called. This is all fine and dandy but I would rather make the call after a small pause allowing the user to type in several characters first. Here is my current code that calls the API after a keyup event: var autocomplete = $('#searchinput').typeahead() .on('keyup', function(ev){ ev.stopPropagation(); ev.preventDefault(); //filter out up/down, tab, enter, and escape keys if( $.inArray(ev.keyCode,[40,38,9,13,27]) === -1 ){ var self = $(this); //set typeahead source to empty self.data('typeahead').source = []; //active used so we aren't triggering duplicate keyup events if( !self.data('active') && self.val().length > 0){ self.data('active', true); //Do data request. Insert your own API logic here. $.getJSON("http://api.rottentomatoes.com/api/public/v1.0/movies.json?callback=?&apikey=MY_API_KEY&page_limit=5",{ q: encodeURI($(this).val()) }, function(data) { //set this to true when your callback executes self.data('active',true); //Filter out your own parameters. Populate them into an array, since this is what typeahead's source requires var arr = [], i=0; var movies = data.movies; $.each(movies, function(index, movie) { arr[i] = movie.title i++; }); //set your results into the typehead's source self.data('typeahead').source = arr; //trigger keyup on the typeahead to make it search self.trigger('keyup'); //All done, set to false to prepare for the next remote query. self.data('active', false); }); } } }); Is it possible to set a small delay and avoid calling the API after every keyup?

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• Rotate MapView in Android

  - by Matthew B.

  I am writing an Android app where one of the features is that the map will rotate according to the compass (i.e. if the phone is pointing east, the map will be oriented so that the east side of the map is on top). Previous answers that I have found suggested over writing the onDraw() method in mapView, however, the api changed the method to final so it cannot be overwritten. As a result I have tried to overwrite the dispatchDraw() method like so: Note: -compass is a boolean that if true, rotate the view -bearing is a float variable that has the degrees that the view should rotate protected void dispatchDraw(Canvas canvas) { canvas.save(); if (compass) { final float w = this.getWidth(); final float h = this.getHeight(); final float scaleFactor = (float)(Math.sqrt(h * h + w * w) / Math.min(w, h)); final float centerX = w / 2.0f; final float centerY = h / 2.0f; canvas.rotate(bearing, centerX, centerY); canvas.scale(scaleFactor, scaleFactor, centerX, centerY); } super.dispatchDraw(canvas); canvas.restore(); }

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• substitution cypher with different alphabet length

  - by seanizer

  I would like to implement a simple substitution cypher to mask private ids in URLs I know how my IDs will look like (combination of upperchase ascii, digits and underscore), and they will be rather long, as they are composed keys. I would like to use a longer alphabet to shorten the resulting codes (I'd like to use upper and lower case ascii letters, digits and nothing else). So my incoming alphabet would be [A-Z0-9_] (37 chars) and my outgoing alphabet would be [A-Za-z0-9] (62 chars) so a compression of almost 50% would be available. let's say my URLs look like this: /my/page/GFZHFFFZFZTFZTF_24_F34 and I want them to look like this instead: /my/page/Ft32zfegZFV5 Obviously both arrays would be shuffled to bring some random order in. This does not have to be secure. if someone figures it out: fine, but I don't want the scheme to be obvious. My desired solution would be to convert the string to an integer representation of radix 37, convert the radix to 62 and use the second alphabet to write out that number. is there any sample code available that does something similar? Integer.parseInt ( http://java.sun.com/javase/6/docs/api/java/lang/Integer.html#parseInt%28java.lang.String,%20int%29 ) has some similar logic, but it is hard-coded to use standard digit behavior Any hints? I am using java to implement this but code or pseudo-code in any other language is of course also helpful

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• Understanding Java Wait and Notify methods

  - by Maddy

  Hello all: I have a following program: import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class SimpleWaitNotify implements Runnable { final static Object obj = new Object(); static boolean value = true; public synchronized void flag() { System.out.println("Before Wait"); try { obj.wait(); } catch (InterruptedException e) { System.out.println("Thread interrupted"); } System.out.println("After Being Notified"); } public synchronized void unflag() { System.out.println("Before Notify All"); obj.notifyAll(); System.out.println("After Notify All Method Call"); } public void run() { if (value) { flag(); } else { unflag(); } } public static void main(String[] args) throws InterruptedException { ExecutorService pool = Executors.newFixedThreadPool(4); SimpleWaitNotify sWait = new SimpleWaitNotify(); pool.execute(sWait); SimpleWaitNotify.value = false; SimpleWaitNotify sNotify = new SimpleWaitNotify(); pool.execute(sNotify); pool.shutdown(); } } When I wait on obj, I get the following exception Exception in thread "pool-1-thread-1" java.lang.IllegalMonitorStateException: current thread not owner for each of the two threads. But if I use SimpleWaitNotify's monitor then the program execution is suspended. In other words, I think it suspends current execution thread and in turn the executor. Any help towards understanding what's going on would be duly appreciated. This is an area1 where the theory and javadoc seem straightforward, and since there aren't many examples, conceptually left a big gap in me.

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• Recursively MySQL Query

  - by Rachel

  How can I implement recursive MySQL Queries. I am trying to look for it but resources are not very helpful. Trying to implement similar logic. public function initiateInserts() { //Open Large CSV File(min 100K rows) for parsing. $this->fin = fopen($file,'r') or die('Cannot open file'); //Parsing Large CSV file to get data and initiate insertion into schema. $query = ""; while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $query = $query + "INSERT INTO dt_table (id, code, connectid, connectcode) VALUES (" + $data[0] + ", " + $data[1] + ", " + $data[2] + ", " + $data[3] + ")"; } $stmt = $this->prepare($query); // Execute the statement $stmt->execute(); $this->checkForErrors($stmt); } @Author: Numenor Error Message: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '0' at line 1 This Approach inspired to look for an MySQL recursive query approach.

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• heterogeneous comparisons in python3

  - by Matt Anderson

  I'm 99+% still using python 2.x, but I'm trying to think ahead to the day when I switch. So, I know that using comparison operators (less/greater than, or equal to) on heterogeneous types that don't have a natural ordering is no longer supported in python3.x -- instead of some consistent (but arbitrary) result we raise TypeError instead. I see the logic in that, and even mostly think its a good thing. Consistency and refusing to guess is a virtue. But what if you essentially want the python2.x behavior? What's the best way to go about getting it? For fun (more or less) I was recently implementing a Skip List, a data structure that keeps its elements sorted. I wanted to use heterogeneous types as keys in the data structure, and I've got to compare keys to one another as I walk the data structure. The python2.x way of comparing makes this really convenient -- you get an understandable ordering amongst elements that have a natural ordering, and some ordering amongst those that don't. Consistently using a sort/comparison key like (type(obj).__name__, obj) has the disadvantage of not interleaving the objects that do have a natural ordering; you get all your floats clustered together before your ints, and your str-derived class separates from your strs. I came up with the following: import operator def hetero_sort_key(obj): cls = type(obj) return (cls.__name__+'_'+cls.__module__, obj) def make_hetero_comparitor(fn): def comparator(a, b): try: return fn(a, b) except TypeError: return fn(hetero_sort_key(a), hetero_sort_key(b)) return comparator hetero_lt = make_hetero_comparitor(operator.lt) hetero_gt = make_hetero_comparitor(operator.gt) hetero_le = make_hetero_comparitor(operator.le) hetero_ge = make_hetero_comparitor(operator.gt) Is there a better way? I suspect one could construct a corner case that this would screw up -- a situation where you can compare type A to B and type A to C, but where B and C raise TypeError when compared, and you can end up with something illogical like a > b, a < c, and yet b > c (because of how their class names sorted). I don't know how likely it is that you'd run into this in practice.

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• a selective dual command binding converter in WPF?

  - by Jippers

  I'll start off and say I am not using the MVVM pattern for my WPF app. Please forgive me. Right now I have a data template with two buttons, each binds to a different command on the CLR object this data template represents. Both use the same command parameter. Here's an example of the buttons. <Button x:Name="Button1" Command="{Binding Path=Command1}" CommandParameter="{Binding Path=Text, ElementName=TextBox1}" /> <Button x:Name="Button2" Command="{Binding Path=Command2}" CommandParameter="{Binding Path=Text, ElementName=TextBox1}" /> I would like to refactor this into a single button that can perform either command based on a user setting like a boolean in Settings.settings. I don't have access to refactoring the CLR object itself. Also this is a Data Template there isn't codebehind for me to work with. My take is that a converter would be the best bet, but I don't know how I would put that together. The converter would need to take in the CommandParameter, as well as the DataContext so it knows which object to execute the Commands on. Can someone lend me a hand with this? Thanks in advance.

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• Combining aggregate functions in an (ANSI) SQL statement

  - by morpheous

  I have aggregate functions foo(), foobar(), fredstats(), barneystats() I want to create a domain specific query language (DSQL) above my DB, to facilitate using using a domain language to query the DB. The 'language' comprises of boolean expressions (or more specifically SQL like criteria) which I then 'translate' back into pure (ANSI) SQL and send to the underlying Db. The following lines are examples of what the language statements will look like, and hopefully, it will help further clarify the concept: **Example 1** DQL statement: foobar('yellow') between 1 and 3 and fredstats('weight') > 42 Translation: fetch all rows in an underlying table where computed values for aggregate function foobar() is between 1 and 3 AND computed value for AGG FUNC fredstats() is greater than 42 **Example 2** DQL statement: fredstats('weight') < barneystats('weight') AND foo('fighter') in (9,10,11) AND foobar('green') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 3** DQL statement: foobar('green') / foobar('red') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 4** DQL statement: foobar('green') - foobar('red') >= 42 Translation: Fetch all rows where the specified criteria matches Given the following information: The table upon which the queries above are being executed is called 'tbl' table 'tbl' has the following structure (id int, name varchar(32), weight float) The result set returns only the tbl.id, tbl.name and the names of the aggregate functions as columns in the result set - so for example the foobar() AGG FUNC column will be called foobar in the result set. So for example, the first DQL query will return a result set with the following columns: id, name, foobar, fredstats Given the above, my questions then are: What would be the underlying SQL required for Example1 ? What would be the underlying SQL required for Example3 ? Given an algebraic equation comprising of AGGREGATE functions, Is there a way of generalizing the algorithm needed to generate the required ANSI SQL statement(s)? I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible.

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