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• Overlay SVG diagrams on google maps

  - by ThibThib

  Hello I would like to add an overlay image on a google map. This image is a SVG file I have generated (python with svgfig). I am using the following code if (GBrowserIsCompatible()) { var map = new GMap2(document.getElementById("map_canvas")); map.setCenter(new GLatLng(48.8, 2.4), 12);     // ground overlay     var boundaries = new GLatLngBounds(new GLatLng(48.283188032632829, 1.9675270369830129), new GLatLng(49.187215000000002, 2.7771877478303999));     var oldmap = new GGroundOverlay("test.svg", boundaries); map.addControl(new GSmallMapControl()); map.addControl(new GMapTypeControl()); map.addOverlay(oldmap); } Surprisingly, it works with Safari 4, but it doesn't with Firefox (with Safari 3, the background is not transparent) Does anyone has an idea on how I could overlay a SVG ? Thanks PS1: I read some works like this or the source code of swa.ethz.ch/googlemaps, but it seems that they have to use javascript code to parse the SVG and add one by one all the elements (but I did not understood all the source...) PS2: The SVG is composed of different filled paths and circles, with transparency. If there is no solution to overlay my SVG, I can use 2 alternative solutions: rasterize the SVG convert the paths and circles in GPolygons But, I do not really like the 1st solution because of the poor quality of the bitmap and the time to generate it with antialiasing. And for the 2nd solutions, the arcs, ellipses and circles will have to be decomposed into small polylines. A lot of them will be necessary for a good result. But I have around 3000 arcs and circles to draw, so...

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• iPhone Core Data problem

  - by Junior B.

  This is my first project with Core Data, I followed the Event tutorial provided by Apple that helped me to understand the basic of core data in iPhone. But now, working over my project, I've a problem adding data into my database. When i create an object and set the data, if I try to get it back, the system returns me a strange sequence of characters. This is what i see in log if I try to log it: 2010-05-11 00:16:43.523 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.525 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.526 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Items: 5 What kind of problem could be this? Edit: This is the part of the code that generate the error: package = (Package *)[NSEntityDescription insertNewObjectForEntityForName:@"Package" inManagedObjectContext:moc]; theNodes = [doc nodesForXPath:@"//pack" error:&error]; for (CXMLElement *theElement in theNodes) { // Create a counter variable as type "int" int counter; // Loop through the children of the current node for(counter = 0; counter < [theElement childCount]; counter++) { if([[[theElement childAtIndex:counter] name] isEqualToString: @"id"]) [package setIdPackage:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"title"]) [package setPackageTitle:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"category"]) [package setCategory:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"lang"]) [package setLang:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"number"]) { NSNumberFormatter * f = [[NSNumberFormatter alloc] init]; [f setNumberStyle:NSNumberFormatterDecimalStyle]; NSNumber * myNumber = [f numberFromString:[[theElement childAtIndex:counter] stringValue]]; [f release]; [package setNumber:myNumber]; } } } NSLog([NSString stringWithFormat:@"=== %s ===\nID: %s\nCategory: %s\nLanguage: %s",[package packageTitle], [package idPackage] ,[package category],[package lang]]);

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• Passing an arbitrary JSONValue to a JSNI function

  - by Riley Lark

  I have a JSONValue in my Java that may be a JSONArray, a JSONObject, a JSONString, etc. I want to pass it to a JSNI function that can accept any of those types. If I naively write my JSNI as something like: public final native jsni(Object parameter) /*-{ doSomething(parameter); }-*/; public void useFunction(JSONValue value) { jsni(value); //Throws js exception at runtime :( } then I get a javascript exception, because GWT doesn't know how to convert the JSONValue to a JavaScriptObject (or native string / number value). My current workaround is public final native jsniForJSO(Object parameter) /*-{ doSomething(parameter); }-*/; public final native jsniForString(String parameter) /*-{ doSomething(parameter); }-*/; public final native jsniForNumber(double parameter) /*-{ doSomething(parameter); }-*/; public actuallyUseFunction(JSONValue value) { if (value.isObject()) { jsniForJSO(value.isObject().getJavaScriptObject()); } else if (value.isString()) { jsniForString(value.isString().stringValue()); } else { //etc } } This is a big burden for code maintainability, etc... especially if you have more than one parameter. Is there a way to generate these functions automatically, or get around this issue altogether? I've taken to wrapping everything in a JSONObject first, so I can definitely get a JavaScriptObject to pass to my jsni, but that's another clumsy mechanic.

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• Scaling Image to multiple sizes for Deep Zoom

  - by AnthonyWJones

  Lets assume I have a bitmap with a square aspect and width of 2048 pixels. In order to create a set of files need by Silverlight's DeepZoomImageTileSource I need to scale this bitmap to 1024 then to 512 then to 256 etc down to 1 pixel image. There are two, I suspect naive, approaches:- For each image required scale the original full size image to the required size. However it seems excessive to be scaling the full image to the very small sizes. Having scaled from one level to the next discard the original image and scale each sucessive scaled image as the source of the next smaller image. However I suspect that this would generate images in the 256-64 range with poor fidelity than using option 1. Note unlike with the Deep Zoom Composer this tool is expected to act in an on-demand fashion hence it needs to complete in a reasonable timeframe (tops 30 seconds). On the pluse side I'm only creating a single multiscale image not a pyramid of mutliple high-res images. I am outside my comfort zone here, any graphics experts got any advice? Am I wrong about point 2? Is point 1 reasonably performant and I'm worrying about nothing? Option 3?

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• Suggestions for entering mobile development -- pure iPhone SDK, Andorid SDK. Mono Touch or Titanium?

  - by Tom Cabanski

  I am entering mobile development. I have been working primarily in .NET since 1.0 came out in beta. Before that, I was mostly a C++ and Delphi guy and still dabble in C++ from time to time. I do web apps quite a bit so I am reasonably proficient with Javascript, JQuery and CSS. I have also done a few Java applications. I started web programming with CGI and live mostly in the ASP.NET MVC world these days. I am trying to decide on which platform/OS and tool to select. I am concerned with the size of the market available for my applications as well as the marketibility of the skills I will pick up. The apps I have in mind would work on both phones and pads. Some aspects of what I have in mind will play better on the bigger screens that will be available on pads. Here are the options I am considering: Apple iPhone/iPad using pure Apple SDK (Objective-C) Apple iPhone/iPad using Mono Touch (C#) Android using pure Android SDK (Java) Multiple platforms using something like Titanium to generate native apps from web technologies (HTML, CSS and Javascript) Multiple platforms using HTML5 web applications that run in the browser (HTML, CSS and Javascript). Which option would you choose? Do you have a different suggestion? What are the pros and cons?

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• Thread Local Memory, Using std::string's internal buffer for c-style Scratch Memory.

  - by Hassan Syed

  I am using Protocol Buffers and OpensSSL to generate, HMACs and then CBC encrypt the two fields to obfuscate the session cookies -- similar Kerberos tokens. Protocol Buffers' API communicates with std::strings and has a buffer caching mechanism; I exploit the caching mechanism, for successive calls in the the same thread, by placing it in thread local memory; additionally the OpenSSL HMAC and EVP CTX's are also placed in the same thread local memory structure ( see this question for some detail on why I use thread local memory and the massive amount of speedup it enables even with a single thread). The generation and deserialization, "my algorithms", of these cookie strings uses intermediary void *s and std::strings and since Protocol Buffers has an internal memory retention mechanism I want these characteristics for "my algorithms". So how do I implement a common scratch memory ? I don't know much about the rdbuf(streambuf - strinbuf ??) of the std::string object. I would presumeably need to grow it to the lowest common size ever encountered during the execution of "my algorithms". Thoughts ? My question I guess would be: " is the internal buffer of a string re-usable, and if so, how ?" Edit: See comments to Vlad's answer please.

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• Database Functional Programming in Clojure

  - by Ralph

  "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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• binding nested json object value to a form field

  - by Jack

  I am building a dynamic form to edit data in a json object. First, if something like this exists let me know. I would rather not build it but I have searched many times for a tool and have found only tree like structures that require entering quotes. I would be happy to treat all values as strings. This edit functionality is for end users so it needs to be easy an not intimidating. So far I have code that generates nested tables to represent a json object. For each value I display a form field. I would like to bind the form field to the associated nested json value. If I could store a reference to the json value I would build an array of references to each value in a json object tree. I have not found a way to do that with javascript. My last resort approach will be to traverse the table after edits are made. I would rather have dynamic updates but a single submit would be better than nothing. Any ideas? // the json in files nests only a few levels. Here is the format of a simple case, { "researcherid_id":{ "id_key":"researcherid_id", "description":"Use to retrieve bibliometric data", "url_template" :[ { "name": "Author Detail", "url": "http://www.researcherid.com/rid/${key}" } ] } } $.get('file.json',make_json_form); function make_json_form(response) { dataset = $.secureEvalJSON(response); // iterate through the object and generate form field for string values. } // Then after the form is edited I want to display the raw updated json (then I want to save it but that is for another thread) // now I iterate through the form and construct the json object // I would rather have the dataset object var updated on focus out after each edit. function show_json(form_id){ var r = {}; var el = document.getElementById(form_id); table_to_json(r,el,null); $('body').html(formattedJSON(r)); }

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• Raw types and subtyping

  - by Dmitrii

  We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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• Packaging reference documentation with jar file

  - by soren.enemaerke

  We are porting our .NET library to a java equivalent and is now looking at how to distribute this port. Packaging the classes into a jar-file seems like best practice and we would then ship this jar file in a zip along with some license terms. But what about the documentation? In .NET land it seems like best practice to distribute the xml file that can be consumed by tooling (Visual Studio) but we can't seem to find such best practices for java. We have javadoc comments on our public classes and interfaces, so we are just looking for a way to generate and distribute these comments in a way that is developer friendly (we're thinking easily consumed from various IDEs). What are developers expecting and how do you best deliver this? We would really prefer to bundle the documentation along with the jar file and not have to host the documentation on our website EDIT: We would like for our documentation to appear inside the java IDEs so we want to provide the documentation in a way that integrates into the IDEs as gracefully as possible. In .NET land this is as an xml file placed next to the .dll file, but is there a similar concept for jar files that enables the integration into tooling? PS: We are developing in Eclipse and have an ant task doing the building and jar-file packaing in our automated build.

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• How to parse rss from a php page, using jQuery/jFeed?

  - by ricebowl

  I'm trying to fumble my way through parsing rss sensibly, using jQuery and jFeed. Because of the same origin policy I'm pulling the BBC's health news feed into a local page (http://www.davidrhysthomas.co.uk/play/proxy.php). Originally this was just the same proxy.php script as available in the jFeed download package, but due to my host's disabling allow_url_fopen() I've amended the php to the following: $url = "http://newsrss.bbc.co.uk/rss/newsonline_uk_edition/health/rss.xml"; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $data = curl_exec($ch); echo "$data"; curl_close($ch); Which seems to generate the same/comparable contents as the original fopen on my local machine. Now that seems to be working, I'm looking at setting the jFeed script up to work with the page and, to my embarrassment, don't see how. I understand that, at the least, this should work: jQuery.getFeed({ url: 'http://www.davidrhysthomas.co.uk/play/proxy.php', success: function(feed) { alert(feed.title); } }); ...but, as I'm sure you anticipate, it doesn't. What non-output there is, is available for your perusal here: http://www.davidrhysthomas.co.uk/play/exampleTest.html. And I honestly don't have a clue what to do about it. If anyone could offer some pointers, tips, hints, or, at a pinch, a quick slap around the cheeks and a 'pull yourself together!' it'd be much appreciated... Thanks in advance =)

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• drawing to a JPanel without inheritance

  - by g.rocket

  Right now I'm working on a program that throws up a bunch of separate (generated at runtime) images, each in their own window. To do this i've tried this approach: public void display(){ JFrame window = new JFrame("NetPart"); JPanel canvas = new JPanel(); window.getContentPane().add(canvas); Graphics g = canvas.getGraphics(); Dimension d = getSize(); System.out.println(d); draw(g,new Point(d.minX*50,d.maxY*50), 50); window.setSize(d.size(50)); window.setResizable(false); window.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE); window.setVisible(true); } public void draw(Graphics g, Point startLoc, int scale){ // generate and draw the image } public Dimension getSize(){ //returns my own dimensions class } However, this throws a NullPointerException in draw, claiming that the graphics is null. is there any way to externally draw to a JPanel from outside it (not inherit from JPanel and override PaintComponent)? Any help would be appreciated.

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• Generating MySQL UPDATE statements containing BLOB image data

  - by Bob

  I'm trying to write an SQL statement that will generate an SQL script that will update a BLOB field with an IMAGE being selected from the database. This is what I have: select concat( 'UPDATE `IMAGE` SET THUMBNAIL = ', QUOTE( THUMBNAIL ), ' WHERE ID = ', ID, ';' ) as UPDATE_STATEMENT from IMAGE; In the above, THUMBNAIL is a BLOB field containing raw image data. When I run the resulting script I get the following error: ERROR at line 2: Unknown command '\\'. I first tried this without the QUOTE() function, like so: select concat( 'UPDATE `IMAGE` SET THUMBNAIL = \'', THUMBNAIL, '\' WHERE ID = ', ID, ';' ) as UPDATE_STATEMENT from IMAGE; Running the resulting script produces this error: ERROR at line 2: Unknown command '\0'. What is the proper function to apply to this BLOB field in the select, so the UPDATE statements will work? If context is required, I'm looking to migrate thumbnails generated on one server to another server for certain image IDs only. I would use mysqldump, but I don't want to clobber the entire table. Any help is greatly appreciated!

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• Having an issue with Nullable MySQL columns in SubSonic 3.0 templates

  - by omegawkd

  Looking at this line in the Settings.ttinclude string CheckNullable(Column col){ string result=""; if(col.IsNullable && col.SysType !="byte[]" && col.SysType !="string") result="?"; return result; } It describes how it determines if the column is nullable based on requirements and returns either "" or "?" to the generated code. Now I'm not too familiar with the ? nullable type operator but from what I can see a cast is required. For instance, if I have a nullable integer MySQL column and I generate the code using the default template files it returns a line similar to this: int? _User_ID; When trying to compile the project I get the error: Cannot implicitly convert type 'int?' to 'int'. An explicit conversion exists (are you missing a cast?) I checked teh Settings files for the other database types and they all seems to have the same routine. So my question is, is this behaviour expected or is this a bug? I need to solve it one way or the other before I can procede. Thanks for your help.

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• Python - Open default mail client using mailto, with multiple recipients

  - by victorhooi

  Hi, I'm attempting to write a Python function to send an email to a list of users, using the default installed mail client. I want to open the email client, and give the user the opportunity to edit the list of users or the email body. I did some searching, and according to here: http://www.sightspecific.com/~mosh/WWW_FAQ/multrec.html It's apparently against the RFC spec to put multiple comma-delimited recipients in a mailto link. However, that's the way everybody else seems to be doing it. What exactly is the modern stance on this? Anyhow, I found the following two sites: http://2ality.blogspot.com/2009/02/generate-emails-with-mailto-urls-and.html http://www.megasolutions.net/python/invoke-users-standard-mail-client-64348.aspx which seem to suggest solutions using urllib.parse (url.parse.quote for me), and webbrowser.open. I tried the sample code from the first link (2ality.blogspot.com), and that worked fine, and opened my default mail client. However, when I try to use the code in my own module, it seems to open up my default browser, for some weird reason. No funny text in the address bar, it just opens up the browser. The email_incorrect_phone_numbers() function is in the Employees class, which contains a dictionary (employee_dict) of Employee objects, which themselves have a number of employee attributes (sn, givenName, mail etc.). Full code is actually here (http://stackoverflow.com/questions/2963975/python-converting-csv-to-objects-code-design) from urllib.parse import quote import webbrowser .... def email_incorrect_phone_numbers(self): email_list = [] for employee in self.employee_dict.values(): if not PhoneNumberFormats.standard_format.search(employee.telephoneNumber): print(employee.telephoneNumber, employee.sn, employee.givenName, employee.mail) email_list.append(employee.mail) recipients = ', '.join(email_list) webbrowser.open("mailto:%s?subject=%s&body=%s" % (recipients, quote("testing"), quote('testing')) ) Any suggestions? Cheers, Victor

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• C# How to perform a live xslt transformation on an in memory object?

  - by JL

  I have a function that takes 2 parameters : 1 = XML file, 2 = XSLT file, then performs a transformation and returns the resulting HTML. Here is the function: /// <summary> /// Will apply an XSLT style to any XML file and return the rendered HTML. /// </summary> /// <param name="xmlFileName"> /// The file name of the XML document. /// </param> /// <param name="xslFileName"> /// The file name of the XSL document. /// </param> /// <returns> /// The rendered HTML. /// </returns> public string TransformXml(string xmlFileName, string xslFileName) { var xtr = new XmlTextReader(xmlFileName) { WhitespaceHandling = WhitespaceHandling.None }; var xd = new XmlDocument(); xd.Load(xtr); var xslt = new System.Xml.Xsl.XslCompiledTransform(); xslt.Load(xslFileName); var stm = new MemoryStream(); xslt.Transform(xd, null, stm); stm.Position = 1; var sr = new StreamReader(stm); xtr.Close(); return sr.ReadToEnd(); } I want to change the function not to accept a file for the XML, but instead just an object. The object is exactly compatible with the xslt, if it was serialized to file. But I don't want to have to serialize it to a file first. So to recap : keep the xslt coming from a file, but the xml input should an object I pass and would like to generate the xml from without any file system interaction.

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• SubSonic generated code and always filtering records

  - by cmroanirgo

  Hi, I have a table called "Users" that has a column called "deleted", a boolean indicating that the user is "Deleted" from the system (without actually deleting it, of course). I also have a lot of tables that have a FK to the Users.user_id column. Subsonic generates (very nicely) the code for all the foreign keys in a similar manner: public IQueryable<person> user { get { var repo=user.GetRepo(); return from items in repo.GetAll() where items.user_id == _user_id select items; } } Whilst this is good and all, is there a way to generate the code in such a way to always filter out the "Deleted" users too? In the office here, the only suggestion we can think of is to use a partial class and extend it. This is obviously a pain when there are lots and lots of classes using the User table, not to mention the fact that it's easy to inadvertently use the wrong property (User vs ActiveUser in this example): public IQueryable<User> ActiveUser { get { var repo=User.GetRepo(); return from items in repo.GetAll() where items.user_id == _user_id and items.deleted == 0 select items; } } Any ideas?

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• XSL-FO: Static content AND Flow content in Region-Body: Possible?

  - by Peterdk

  I have the following problem: I need to use XSLFO to generate a 2-column multipage document. Problem is: I need to have a vertical line between the 2 columns. Since XSLFO does not seem to specify a option for creating such a divider, I need to manually put it there. I was thinking of using a static rotated blockcontainer with a leader in it. However, it looks like it's not possible to use static-content on the same region as where the flow content comes. <fo:layout-master-set> <fo:simple-page-master page-width="170mm" page-height="222mm" master-name="page" > <fo:region-body region-name="xsl-region-body" margin-top="2mm" margin-bottom="2mm" margin-left="10mm" margin-right="10mm" column-count="2" column-gap="5mm" /> </fo:simple-page-master> </fo:layout-master-set> <fo:page-sequence master-reference="page"> <fo:static-content flow-name="xsl-region-body" ><!-- This gives a error --> <fo:block>test</fo:block> </fo:static-content> <fo:flow flow-name="xsl-region-body"> <xsl:apply-templates/> </fo:flow> </fo:page-sequence> Results in (XEP): [error] Duplicate identifier: flow-name="xsl-region-body". Property 'flow-name' should be unique within 'fo:page-sequence'. Are there any methods to place static content on the main region when also flow content is placed there? Or: Is there a way to define the divider that divides a 2-column layout?

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• Improving field get and set performance with ASM or Javassist

  - by ng

  I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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• Can parser combinators be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• Add gridlines to a output plot in Mathemaitca

  - by xslittlegrass

  I'm trying to add gridlines to a output density plot in Mathematica. The plot is generated by a long calculation in Mathematica and when I do the plot I forget to add the Mesh-True options. I don't want to do all the calculation and generate the plot again since it takes a long time. Is that possible to add the gridlines or mesh lines to plot ONLY using the output plot at hand? For example, If I have a plot p. Is it possible to add the mesh lines ONLY manipulate p? In a ordinary one dimensional plot, this will work p1 = Plot[Sin[x], {x, -3, 3}]; Insert[p1, GridLines -> Automatic, -1] But when I try the density plot, it seems the gridlines is always under the plot, and can be seen only at the image margin area. p2 = DensityPlot[Sin[x + y^2], {x, -3, 3}, {y, -2, 2}, PlotRangePadding -> 0.2]; Insert[p2, GridLines -> Automatic, -1] Updata The Mesh option on the output plot will not work because Mesh is not a options of a Graphics: Show[p2,Mesh->True] will give a message "an unrecoginzed option name(Mesh) was encountered while rendering a Graphics" Thanks.

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• problem loading texture with transparency with OpenGL ES and Android

  - by Evan Kimia

  Im trying to load an image that has background transparency that will be layered over another texture. When i try and load it, all i get is a white screen. The texture is 512 by 512, and its saved in photoshop as a 24 bit PNG (standard PNG specs in the Photoshop Save for Web and Devices config window). Any idea why its not showing? The texture without transparency shows without a problem. Here is my loadTextures method: public void loadGLTexture(GL10 gl, Context context) { //Get the texture from the Android resource directory Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.m1); Bitmap normalScheduleLines = BitmapFactory.decodeResource(context.getResources(), R.drawable.m1n); //Generate texture pointers... gl.glGenTextures(3, textures, 0); //...and bind it to our array gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[1]); //Create Nearest Filtered Texture gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR_MIPMAP_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL11.GL_TEXTURE_2D, GL11.GL_GENERATE_MIPMAP, GL11.GL_TRUE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0); bitmap.recycle(); //Bind our normal schedule bus map lines gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]); //Create Nearest Filtered Texture gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR_MIPMAP_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL11.GL_TEXTURE_2D, GL11.GL_GENERATE_MIPMAP, GL11.GL_TRUE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GL10.GL_RGBA, normalScheduleLines, 0); normalScheduleLines.recycle(); }

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• Trying to write up a C daemon, but don't know enough C to continue

  - by JamesM-SiteGen

  Okay, so I want this daemon to run in the background with little to no interaction. I plan to have it work with Apache, lighttpd, etc to send the session & request information to allow C to generate a website from an object DB, saving will have to be an option so, you can start the daemon with an existing DB but will not save to it unless you login to the admin area and enable, and restart the daemon. Summary of the daemon: Load a database from file. Have a function to restart the daemon. Allow Apache, lighttpd, etc to get necessary data about the request and session. A varible to allow the database to be saved to the file, otherwise it will only be stored in ram. If it is set to save back to the file, then only have neccessary data in ram. Use sql-light for the database file. Build a webpage from some template files. $(myVar) for getting variables. Get templates from a directory. ./templates/01-test/{index.html,template.css,template.js} Live version of the code and more information: http://typewith.me/YbGB1h1g1p Also I am working on a website CMS in php, but I am tring to switch to C as it is faster than php. ( php is quite fast, but the fact that making a few mySQL requests for every webpage is quite unefficent and I'm sure that it can be far better, so an object that we can recall data from in C would have to be faster ) P.S I am using Arch-Linux not MS-Windows, with the package group base-devel for the common developer tools such as make and makepgk. Edit: Oupps, forgot the question ;) Okay, so the question is, how can I turn this basic C daemon into a base to what I am attempting to do here?

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• Java: how to tell if a line in a text file was supposed to be blank?

  - by defn

  I'm working on a project in which I have to read in a Grammar file (breaking it up into my data structure), with the goal of being able to generate a random "DearJohnLetter". My problem is that when reading in the .txt file, I don't know how find out whether the file was supposed to be a completely blank line or not, which is detrimental to the program. Here is an example of part of the file, How do i tell if the next line was supposed to be a blank line? (btw I'm just using a buffered reader) Thanks! <start> I have to break up with you because <reason> . But let's still <disclaimer> . <reason> <dubious-excuse> <dubious-excuse> , and also because <reason> <dubious-excuse> my <person> doesn't like you I'm in love with <another> I haven't told you this before but <harsh> I didn't have the heart to tell you this when we were going out, but <harsh> you never <romantic-with-me> with me any more you don't <romantic> any more my <someone> said you were bad news

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• How do I sign requests reliably for the Last.fm api in C#?

  - by Arda Xi

  I'm trying to implement authorization through Last.fm. I'm submitting my arguments as a Dictionary to make the signing easier. This is the code I'm using to sign my calls: public static string SignCall(Dictionary<string, string> args) { IOrderedEnumerable<KeyValuePair<string, string>> sortedArgs = args.OrderBy(arg => arg.Key); string signature = sortedArgs.Select(pair => pair.Key + pair.Value). Aggregate((first, second) => first + second); return MD5(signature + SecretKey); } I've checked the output in the debugger, it's exactly how it should be, however, I'm still getting WebExceptions every time I try. Here's my code I use to generate the URL in case it'll help: public static string GetSignedURI(Dictionary<string, string> args, bool get) { var stringBuilder = new StringBuilder(); if (get) stringBuilder.Append("http://ws.audioscrobbler.com/2.0/?"); foreach (var kvp in args) stringBuilder.AppendFormat("{0}={1}&", kvp.Key, kvp.Value); stringBuilder.Append("api_sig="+SignCall(args)); return stringBuilder.ToString(); } And sample usage to get a SessionKey: var args = new Dictionary<string, string> { {"method", "auth.getSession"}, {"api_key", ApiKey}, {"token", token} }; string url = GetSignedURI(args, true); EDIT: Oh, and the code references an MD5 function implemented like this: public static string MD5(string toHash) { byte[] textBytes = Encoding.UTF8.GetBytes(toHash); var cryptHandler = new System.Security.Cryptography.MD5CryptoServiceProvider(); byte[] hash = cryptHandler.ComputeHash(textBytes); return hash.Aggregate("", (current, a) => current + a.ToString("x2")); }

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