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• What makes people think that NNs have more computational power than existing models?

  - by Bubba88

  I've read in Wikipedia that neural-network functions defined on a field of arbitrary real/rational numbers (along with algorithmic schemas, and the speculative `transrecursive' models) have more computational power than the computers we use today. Of course it was a page of russian wikipedia (ru.wikipedia.org) and that may be not properly proven, but that's not the only source of such.. rumors Now, the thing that I really do not understand is: How can a string-rewriting machine (NNs are exactly string-rewriting machines just as Turing machines are; only programming language is different) be more powerful than a universally capable U-machine? Yes, the descriptive instrument is really different, but the fact is that any function of such class can be (easily or not) turned to be a legal Turing-machine. Am I wrong? Do I miss something important? What is the cause of people saying that? I do know that the fenomenum of undecidability is widely accepted today (though not consistently proven according to what I've read), but I do not really see a smallest chance of NNs being able to solve that particular problem. Add-in: Not consistently proven according to what I've read - I meant that you might want to take a look at A. Zenkin's (russian mathematician) papers after mid-90-s where he persuasively postulates the wrongness of G. Cantor's concepts, including transfinite sets, uncountable sets, diagonalization method (method used in the proof of undecidability by Turing) and maybe others. Even Goedel's incompletness theorems were proven in right way in only 21-st century.. That's all just to plug Zenkin's work to the post cause I don't know how widespread that knowledge is in CS community so forgive me if that did look stupid. Thank you!

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• Rails: creating a custom data type, to use with generator classes and a bunch of questions related t

  - by Shyam

  Hi, After being productive with Rails for some weeks, I learned some tricks and got some experience with the framework. About 10 days ago, I figured out it is possible to build a custom data type for migrations by adding some code in the Table definition. Also, after learning a bit about floating points (and how evil they are) vs integers, the money gem and other possible solutions, I decided I didn't WANT to use the money gem, but instead try to learn more about programming and finding a solution myself. Some suggestions said that I should be using integers, one for the whole numbers and one for the cents. When playing in script/console, I discovered how easy it is to work with calculations and arrays. But, I am talking to much (and the reason I am, is to give some sufficient background). Right now, while playing with the scaffold generator (yes, I use it, because I like they way I can quickly set up a prototype while I am still researching my objectives), I like to use a DRY method. In my opinion, I should build a custom "object", that can hold two variables (Fixnum), one for the whole, one for the cents. In my big dream, I would be able to do the following: script/generate scaffold Cake name:string description:text cost:mycustom Where mycustom should create two integer columns (one for wholes, one for cents). Right now I could do this by doing: script/generate scaffold Cake name:string description:text cost_w:integer cost_c:integer I had also had an idea that would be creating a "cost model", which would hold two columns of integers and create a cost_id column to my scaffold. But wouldn't that be an extra table that would cause some kind of performance penalty? And wouldn't that be defy the purpose of the Cake model in the first place, because the costs are an attribute of individual Cake entries? The reason why I would want to have such a functionality because I am thinking of having multiple "costs" inside my rails application. Thank you for your feedback, comments and answers! I hope my message got through as understandable, my apologies for incorrect grammar or weird sentences as English is not my native language.

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• how does one _model_ data from relational databases in clojure ?

  - by sandeep

  I have asked this question on twitter as well the #clojure IRC channel, yet got no responses. There have been several articles about Clojure-for-Ruby-programmers, Clojure-for-lisp-programmers.. but what is the missing part is Clojure for ActiveRecord programmers . There have been articles about interacting with MongoDB, Redis, etc. - but these are key value stores at the end of the day. However, coming from a Rails background, we are used to thinking about databases in terms of inheritance - has_many, polymorphic, belongs_to, etc. The few articles about Clojure/Compojure + MySQL (ffclassic) - delve right into sql. Of course, it might be that an ORM induces impedence mismatch, but the fact remains that after thinking like ActiveRecord, it is very difficult to think any other way. I believe that relational DBs, lend themselves very well to the object-oriented paradigm because of them being , essentially, Sets. Stuff like activerecord is very well suited for modelling this data. For e.g. a blog - simply put class Post < ActiveRecord::Base has_many :comments end class Comment < ActiveRecord::Base belongs_to :post end How does one model this in Clojure - which is so strictly anti-OO ? Perhaps the question would have been better if it referred to all functional programming languages, but I am more interested from a Clojure standpoint (and Clojure examples)

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• Using pointers to adjust global objects in objective-c

  - by Rob

  Ok, so I am working with two sets of data that are extremely similar, and at the same time, these data sets are both global NSMutableArrays within the object. data_set_one = [[NSMutableArray alloc] init]; data_set_two = [[NSMutableArray alloc] init]; Two new NSMutableArrays are loaded, which need to be added to the old, existing data. These Arrays are also global. xml_dataset_one = [[NSMutableArray alloc] init]; xml_dataset_two = [[NSMutableArray alloc] init]; To reduce code duplication (and because these data sets are so similar) I wrote a void method within the class to handle the data combination process for both Arrays: -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str Now, I have a decent understanding of object oriented programming, so I was thinking that if I were to invoke the method with the global Arrays in the data like so... [self constructData:data_set_one fromDownloadArray:xml_dataset_one withMatchSelector:@"id"]; Then the global NSMutableArrays (data_set_one) would reflect the changes that happen to "array" within the method. Sadly, this is not the case, data_set_one doesn't reflect the changes (ex: new objects within the Array) outside of the method. Here is a code snippet of the problem // data_set_one is empty // xml_dataset_one has a few objects [constructData:(NSMutableArray *)data_set_one fromDownloadArray:(NSMutableArray *)xml_dataset_one withMatchSelector:(NSString *)@"id"]; // data_set_one should now be xml_dataset_one, but when echoed to screen, it appears to remain empty And here is the gist of the code for the method, any help is appreciated. -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str { if ([data count] == 0) { data = down; // set data equal to downloaded data } else if ([down count] == 0) { // download yields no results, do nothing } else { // combine the two arrays here } } This project is not ARC enabled. Thanks for the help guys! Rob

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• Deploy an hta file in an exe or msi file

  - by rjmunro

  I've written an HTA file frontend for our web app that allows the web app to run without web browser status bars etc, and allows it to access the local system for certain tasks. I need a way to deploy this to customers. I need an installer to supply an hta file, an ico file, and add a link to them in the start menu and on the users desktop. I looked at building an installer with NSIS, but I couldn't figure out how to assign the icon to the shortcuts - The icon had to be a standard HTA one. Can this be done with NSIS, or should I be using another installer? P.s. I've got no particular preference for NSIS, it's just something I once used a very long time ago. When I download stuff, I think I prefer them to be msi files that launch with windows installer (it feels more like downloading a .rpm or .deb on linux which I am used to) but I know nothing about how those are created. I'm a web/linux guy who knows very little about windows programming.

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• PHP Commercial Project Function define

  - by Shiro

  Currently I am working with a commercial project with PHP. I think this question not really apply to PHP for all programming language, just want to discuss how your guys solve it. I work in MVC framework (CodeIgniter). all the database transaction code in model class. Previously, I seperate different search criteria with different function name. Just an example function get_student_detail_by_ID($id){} function get_student_detail_by_name($name){} as you can see the function actually can merge to one, just add a parameter for it. But something you are rushing with project, you won't look back previously got what similar function just make some changes can meet the goal. In this case, we found that there is a lot function there and hard to maintenance. Recently, we try to group the entity to one ultimate search something like this function get_ResList($is_row_count=FALSE, $record_start=0, $arr_search_criteria='', $paging_limit=20, $orderby='name', $sortdir='ASC') we try to make this function to fit all the searching criteria. However, our system getting bigger and bigger, the search criteria not more 1-2 tables. It require join with other table with different purpose. What we had done is using IF ELSE, if(bla bla bla) { $sql_join = JOIN_SOME_TABLE; $sql_where = CONDITION; } at the end, we found that very hard to maintance the function. it is very hard to debug as well. I would like to ask your opinion, what is the commercial solution they solve this kind of issue, how to define a function and how to revise it. I think this is link project management skill. Hope you willing to share with us. Thanks.

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• Python function correctly/incorrectly?

  - by Anthony Kernan

  I'm just starting too use python, learning experience. I know the basics logic of programming. I have a function in python that is running everytime, even when it's not supposed to. I use an if statement in the beginning of the function. I don't know why this if statement is not working, confused. I have another function that is similar and works correctly. Am I missing something simple? Here's the function that is not working... def check_artist_art(): if os.path.exists("/tmp/artistinfo") and open("/tmp/artistinfo").read() != title: #if artist == "": if os.path.exists(home + "/.artist"): os.remove(home + "/.artist") if os.path.exists("/tmp/artistinfo"): os.remove("/tmp/artistinfo") print artist return False else: os.path.exists("/tmp/artistinfo") and open("/tmp/artistinfo").read() == artist return False return True And this is the similar function that is working correctly.. def check_album(): if os.path.exists("/tmp/albuminfo") and open("/tmp/albuminfo").read() != album: if os.path.exists(home + "/.album"): os.remove(home + "/.album") if os.path.exists("/tmp/albuminfo"): os.remove("/tmp/albuminfo") return False elif os.path.exists("/tmp/trackinfo") and open("/tmp/trackinfo").read() == artist + album: return False return True Any help is greatly appreciated.

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• Why is debugging better in an IDE?

  - by Bill Karwin

  I've been a software developer for over twenty years, programming in C, Perl, SQL, Java, PHP, JavaScript, and recently Python. I've never had a problem I could not debug using some careful thought, and well-placed debugging print statements. I respect that many people say that my techniques are primitive, and using a real debugger in an IDE is much better. Yet from my observation, IDE users don't appear to debug faster or more successfully than I can, using my stone knives and bear skins. I'm sincerely open to learning the right tools, I've just never been shown a compelling advantage to using visual debuggers. Moreover, I have never read a tutorial or book that showed how to debug effectively using an IDE, beyond the basics of how to set breakpoints and display the contents of variables. What am I missing? What makes IDE debugging tools so much more effective than thoughtful use of diagnostic print statements? Can you suggest resources (tutorials, books, screencasts) that show the finer techniques of IDE debugging? Sweet answers! Thanks much to everyone for taking the time. Very illuminating. I voted up many, and voted none down. Some notable points: Debuggers can help me do ad hoc inspection or alteration of variables, code, or any other aspect of the runtime environment, whereas manual debugging requires me to stop, edit, and re-execute the application (possibly requiring recompilation). Debuggers can attach to a running process or use a crash dump, whereas with manual debugging, "steps to reproduce" a defect are necessary. Debuggers can display complex data structures, multi-threaded environments, or full runtime stacks easily and in a more readable manner. Debuggers offer many ways to reduce the time and repetitive work to do almost any debugging tasks. Visual debuggers and console debuggers are both useful, and have many features in common. A visual debugger integrated into an IDE also gives you convenient access to smart editing and all the other features of the IDE, in a single integrated development environment (hence the name).

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• Print an array elements

  - by 1ace1

  Hello guys, this is my first post and im still a beginner in the programming world so bare with me. I just created an array with 100 initialized values and i want to print out 10 elements on each line so it would be somthing like this 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ...26 this is the code i used and i managed to do it for the first 10 elements but i couldnt figure out how to do it for the rest public static void main(String[] args) { int[] numbers = { 0,1,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17}; int i, count = 0; for (i = 0; i < numbers.length; i++) { System.out.print(numbers[i] + " "); count++; if (count == 9) for (i = 9; i < numbers.length; i++) System.out.println(numbers[i] + " "); } } thanks!

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• How do I update a NSTableView when its data source has changed?

  - by Jergason

  I am working along with Cocoa Programming For Mac OS X (a great book). One of the exercises the book gives is to build a simple to-do program. The UI has a table view, a text field to type in a new item and an "Add" button to add the new item to the table. On the back end I have a controller that is the data source and delegate for my NSTableView. The controller also implements an IBAction method called by the "Add" button. It contains a NSMutableArray to hold the to do list items. When the button is clicked, the action method fires correctly and the new string gets added to the mutable array. However, my data source methods are not being called correctly. Here they be: - (NSInteger)numberOfRowsInTableView:(NSTableView *)aTableView { NSLog(@"Calling numberOfRowsInTableView: %d", [todoList count]); return [todoList count]; } - (id)tableView:(NSTableView *)aTableView objectValueForTableColumn:(NSTableColumn *)aTableColumn row:(NSInteger)rowIndex { NSLog(@"Returning %@ to be displayed", [todoList objectAtIndex:rowIndex]); return [todoList objectAtIndex:rowIndex]; } Here is the rub. -numberOfRowsInTableView only gets called when the app first starts, not every time I add something new to the array. -objectValueForTableColumn never gets called at all. I assume this is because Cocoa is smart enough to not call this method when there is nothing to draw. Is there some method I need to call to let the table view know that its data source has changed, and it should redraw itself?

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• Developing Job References

  - by Joe Smith

  How do you develop references for jobs? I have 6 years of programming experience spanning two jobs, but sadly I don't have a lot of people I can draw on as references. It's been several years since I left my last job, which was at a small company, and I've lost touch with the few people I knew there. I now work at another small company. I think I've gone as far as I can in my current position, and would like to look for greener pastures, but I can't exactly use my current boss as a reference, even though I have a very good repore with him. I'm sure he'd make a great reference down the road, but I'm afraid I'd insult him or jeopardize my current job by mentioning that I'm thinking of leaving and would like him to help me. I've applied to some jobs, and I have gotten several replies like, "Oh, you're exactly what we're looking for. Send us a couple references and we'll schedule an interview. Oh, no references? You must be a psychopath, nevermind." I've tried doing some small freelance work on the side, just so I can have a contact who can vouch for my work, but the competition for even small projects is pretty fierce and I can rarely devote adequate time to freelancing while holding a full time job. In addition, I often encounter a Catch-22 where a lot of freelancing jobs also require references. So how do programmers maintain existing references and develop new ones, especially while holding a full time job?

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• How to add deploy.jar to classpath?

  - by dma_k

  I am facing the problem: I need to add ${java.home}/lib/deploy.jar JAR file to classpath in the runtime (dynamically from java). The solution with Thread#setContextClassLoader(ClassLoader) (mentioned here) does not work because of this bug (if somebody can explain what is really a problem – you are welcome). The solution with -Xbootclasspath/a:"%JAVA_HOME%/jre/lib/deploy.jar" does not work well for me, because I want to have "pure executable jar" as a deliverable: no wrapping scripts please (more over %JAVA_HOME% may not be defined in user's environment in Windows for example, plus I need to write a script per platform) The solution with merging deploy.jar file into my deliverable works only if I make a build on Windows platform. Unfortunately, when the deliverable is produced on build server running on Linux, I got Linux-dependant JAR, which does not execute on Windows – it fails with the trace below. I have read How the Java Launcher Finds Classes and Java programming dynamics: Java classes and class loading articles but I've got no extra ideas, how to correctly handle this situation. Any advices or solutions are very welcomed. Trace: java.lang.NoClassDefFoundError: Could not initialize class com.sun.deploy.config.Config at com.sun.deploy.net.proxy.UserDefinedProxyConfig.getBrowserProxyInfo(UserDefinedProxyConfig.java:43) at com.sun.deploy.net.proxy.DynamicProxyManager.reset(DynamicProxyManager.java:235) at com.sun.deploy.net.proxy.DeployProxySelector.reset(DeployProxySelector.java:59) ... java.lang.NullPointerException at com.sun.deploy.net.proxy.DynamicProxyManager.getProxyList(DynamicProxyManager.java:63) at com.sun.deploy.net.proxy.DeployProxySelector.select(DeployProxySelector.java:166)

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• Combining the jquery Calendar picker with the jquery validation and getting them to play nice?

  - by MBonig

  I'm just starting to get into jquery/javascript programming so this may be a beginner question but I sure can't seem to find anything about it. I have a text field on a form. I've used the JQuery UI Calendar picker to make data entry better. I've also added jquery validation to ensure that if the user enters the date by hand that it's still valid. Here is the html: <input class="datepicker" id="Log_ServiceStartTime_date" name="Log_ServiceStartTime_date" type="text" value="3/16/2010"></input> and javascript: $('form').validate(); $('#Log_ServiceStartTime_date').rules('add','required'); $('#Log_ServiceStartTime_date').rules('add','date'); the problem I'm having is this: If a user puts in a bad date, or no date at all, the validation correctly kicks in and the error description displays. However, if the user clicks on the textbox to bring up the calendar picker and selects a date, the date fills into the field but the validation does not go away. If the user clicks into the textbox and then back out, the validation correctly goes away. How can I get the calendar picker to kick off the validation routine once a date is selected? thanks

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• VC++ 6 and MS Speech SDK 5.1 fatal error C1083: Cannot open source file: 'files\microsoft': No such

  - by eg123

  Trying to compile an application (flite synthesis sapi) on vc++6. This requires Microsoft Speech SDK 5.1 Have included C:\Program Files\Microsoft Speech SDK 5.1\IDL C:\Program Files\Microsoft Speech SDK 5.1\include using Toolsoptionsdirectories and also on another attempt via ProjectSettings Repeatedly get this error microsoft fatal error C1083: Cannot open source file: 'files\microsoft': No such file or directory speech fatal error C1083: Cannot open source file: 'speech': No such file or directory sdk fatal error C1083: Cannot open source file: 'sdk': No such file or directory idl fatal error C1083: Cannot open source file: '5.1\idl': No such file or directory FliteCMUKalDiphone.idl Thought it may be spaces related so included full path in quotes in relevant .h files. No joy Installed Microsoft Speech SDK 5.1 on another machine in same folder as flite and renamed to mssdk51 (so no spaces in pathname) but same error came up. Tried pasting in contents of each .idl called in file where glitch seems to generate Still same message. I am new to C++ and programming in general. My only guess is that something in the speech sdk is calling the .idl file and I can't find where from. Of course this is probably way wrong!

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• How do you make life easier for yourself when developing a really large database

  - by Hannes de Jager

  I am busy developing 2 web based systems with MySql databases and the amount of tables/views/stored routines is really becoming a lot and it is more and more challenging to handle the complexity. Now in programming languages we have namespacing e.g. Java packages, C++ namespaces to partition the software, grouping it together to make things more understandable. Databases on the other hand have more of a flat structure (MySql at least) e.g. tables and stored procedures are on the same level. So one have to be more creative, creating naming conventions, perhaps use more than one database or using tools to visualize things. What methods do you use to ease the pain? To be effective while developing your databases? To not get lost in a sea of tables and fields and stored procs? Feel free to mention tools you use also, but try to restrict it to open source and preferably Linux solutions if thats OK. b.t.w How many tables would a database have to be considered large in terms of design?

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• Can you open a form or window in an Outlook Addin (VSTO)

  - by dontpanic

  Hi, I am new to VSTO programming. I have created a basic addin for Outlook 2007 that monitors a folder containing XML text files which it opens and then sends them as an email, then deletes them. this all works fine. I want the user to be able to configure certain settings for the way the addin/program will operate, such as the folder that it will monitor, and other things. The logical way to do this is to create a menu item in the addin (which I have also done) that opens a windows form (or XAML window) that allows them to enter the parameters. In my addin I added a new item Windows Form, which worked, and the designer opened. However, in my addin code I cannot open the form. The Show() method normally associated with form objects is not available. Is this simply something you cannot do, or am I just doing it the wrong way? I have read about Outlook form regions, but these seemed to be attached to outlook items such as a new email, task, appointment etc... there doesnt seem to be a way to create a form region that can be opened in the main window of Outlook. Ideally, I would like to go with my original method of opening a new window from a menu item, but if this isnt possible I would like to hear other solutions. Thanks, Will.

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• How do I get into a career as a programmer/development DBA?

  - by markle976

  About 8-9 years ago I started getting into programming as a hobby. I started with my TI-86 calculator, and then moved into using Visual Basic. After about a year I started playing around with HTML and JavaScript. Then I discovered Flash; I programmed with Actionscript 2.0 for about 2 years which lead me to start using Coldfusion. After a while I realized that A) I am not a designer, and B) with the way that things were going with AJAX, .NET, and PHP there wasn’t much future in Coldfusion/Actionscript. I had been working mostly as an administrative assistant, but about 3-4 years ago I got a position where I would be doing some web development, and assisting the system admin with supporting windows desktop PCs. I have gotten some decent experience over the past few years, but it has been spread out in somewhat disparate areas: I spend about 40% of my time writing PHP/MySQL and HTML/CSS, etc. I spend about 20% of my time helping users with PC questions. I spend about 20% of my time doing administrative things (mail-merges, excel, etc). I spend about 20% of my time managing / creating reports from our Access Database. I have also taught myself many things on my own, and now have a beginner’s level understanding of things like: Windows Server, Java, Linux, Objective-C, SQL Server, C#, C++, Ruby, Mac OSX, VBA, VBScript, and basic IP networks. I feel like I am in a bit of a rut – I want to get my career moving, but I am not sure what I need to do. If I practice with C# and SQL Server Express for a year will that be enough to get me in the door somewhere? Would it be easier to get a position if I teach myself Linux/Apache since I have more experience with PHP/MySQL?

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• How to use python to create a GUI application which have cool animation/effects under Linux (like 3D

  - by sgon00

  Hi, I am not sure if my question title makes sense to you or not. I am seeing many cool applications which have cool animations/effects. I would like to learn how to use python to create this kind of GUI applications under Linux. "cool animation/effects" like 3D wall in Cooliris which is written in flash and compiz effects with opengl. I also heard of some python GUI library like wxPython and pyQT. Since I am completely new to python GUI programming, can anyone suggest me where to start and what I should learn to achieve and create such application? maybe learn pyQT with openGL feature? pyopengl binding? I have no clue on where to start. thank you very much for your time and suggestion. By the way, in case if someone need to know which kind of application I am going to create, well, just any kind of applications. maybe photo explorer with 3D wall, maybe IM client, maybe facebook client etc...

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• Midiplayer stops playing sounds after 16 notes.

  - by user349673

  Hi. I am currently programming a Piano Keyboard editor, much like the one you can find in Cubase, Logic, Reason etc.. I have this big grid, double array new int [13][9], which makes it 13 rows, 9 columns. The first column [0-12][0] is the Keyboard, at the top there's "high C" (midi note 72) and at the bottom there's "low C" (midi note 60). That column is an array of JButtons and when you press for example "low C", note 60 is being played by the Synthesizer. I've gotten this to work pretty OK as for now, but one problem I have is that I can only play 16 notes in a row, then it's like the Synthesizer shuts down or something. Do you guys have ANY idea of what the problem is? A bit of the code: import java.awt.*; import javax.swing.*; import java.awt.event.*; import java.util.*; import javax.sound.midi.*; actionPerformed(ActionEvent ae){ for(int i = 0; i<13; i++){ if(o== instr[i]){//instr is the button array SpelaTangent(i); } } } public void SpelaTangent(int tangent){ int [] klaviatur = new int[13]; for(int i = 0; i<13; i++){ klaviatur[i] = (72-i); } try { Synthesizer synth = MidiSystem.getSynthesizer(); synth.open(); final MidiChannel[] mc = synth.getChannels(); Instrument[] instrument = synth.getDefaultSoundbank().getInstruments(); synth.loadInstrument(instrument[1]); mc[0].noteOn(klaviatur[tangent],350); mc[0].noteOff(klaviatur[tangent],350); } catch (MidiUnavailableException e) {} } Help is very much appreciated!

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• pdf external streams in Max OS X Preview

  - by olpa

  According to the specification, a part of a PDF document can reside in an external file. An example for an image: 2 0 obj << /Type /XObject /Subtype /Image /Width 117 /Height 117 /BitsPerComponent 8 /Length 0 /ColorSpace /DeviceRGB /FFilter /DCTDecode /F (pinguine.jpg) >> stream endstream endobj I found that this functionality does work in Adobe Acrobat 5.0 for Windows (sample PDF with the image), also I managed to view this file in Adobe Acrobat Reader 8.1.3 for Mac OS X after I found the setting "Allow external content". Unfortunately, it seems that non-Adobe tools ignore the external stream feature. I hope I'm wrong, therefore ask the question: How to enable external streams in Mac OS X? (I think that all the system Mac OS X tools use the same library, therefore say "Mac OS X" instead of "Preview".) Or maybe there could be a programming hook to emulate external streams? My task is: store a big set of images (total ˜300Mb) outside of a small PDF (˜1Mb). At some moment, I want to filter PDF through a quartz filter and get a PDF with the images embedded. Any suggestions are welcome.

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• Secure Copy File from remote server via scp and os module in Python

  - by user1063572

  I'm pretty new to Python and programming. I'm trying to copy a file between two computers via a python script. However the code os.system("ssh " + hostname + " scp " + filepath + " " + user + "@" + localhost + ":" cwd) won't work. I think it needs a password, as descriped in How do I copy a file to a remote server in python using scp or ssh?. I didn't get any error logs, the file just won't show in my current working directory. However every other command with os.system("ssh " + hostname + "command") or os.popen("ssh " + hostname + "command") does work. - command = e.g. ls When I try ssh hostname scp file user@local:directory in the commandline it works without entering a password. I tried to combine os.popen commands with getpass and pxssh module to establish a ssh connection to the remote server and use it to send commands directly (I only tested it for an easy command): import pxssh import getpass ssh = pxssh.pxssh() ssh.force_password = True hostname = raw_input("Hostname: ") user = raw_input("Username: ") password = getpass.getpass("Password: ") ssh.login(hostname, user, password) test = os.popen("hostname") print test But I'm not able to put commands through to the remote server (print test shows, that hostname = local and not the remote server), however I'm sure, the conection is established. I thought it would be easier to establish a connection than always use "ssh " + hostname in the bash commands. I also tried some of the workarounds in How do I copy a file to a remote server in python using scp or ssh?, but I must admit due to lack of expirience I didn't get them to work. Thanks a lot for helping me.

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• How to update GUI thread/class from worker thread/class?

  - by user315182

  First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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• Python modules not updating after restarting the main module.

  - by Ian

  I've recently come back to a project having had to stop for about 6 months, and after reinstalling my operating system and coming back to it I'm having all kinds of crazy things happen. I made sure to install the same version(2.6) of python that I was using before. It started by giving me strange tkinter error that I hadn't had trouble with before, the program is relatively simple and the 2 or 3 bugs that were left when i quit, I had documented and weren't related to the interface. Things got even weirder when the same error would pop up even after I had removed the offending section of code. In fact, the traceback pointed to a line that didn't even exist in the module it was referencing, eg: line 262 when the module was only 200 lines long. After just starting a completely new file for the main module and copy/pasting it finally recognized that the offending code was gone and I stopped getting the error only to find that any updates to the code I made in another module didn't show up when I restarted the program through the shell. (I didn't forget to save.) After fiddling with this, of course, the old interface error came back, only in a different section of code that had been working previously. In fact, if I revert back to the files I had six months ago, the program works fine. As soon as I change anything in the main module, however, the interface bug comes back. Here's the original error: Exception in Tkinter callback Traceback (most recent call last): File "C:\Python26\lib\lib-tk\Tkinter.py", line 1410, in __call__ return self.func(*args) File "C:\PyStuff\interface.py", line 202, in dispOne __main__.top.destroy() File "C:\Python26\lib\lib-tk\Tkinter.py", line 1938, in destroy self.tk.call('destroy', self._w) TclError: can't invoke "destroy" command: application has been destroyed I'm guessing something else is going on here other than my own poor programming. Anyone have any ideas?

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• Endianness and C API's: Specifically OpenSSL.

  - by Hassan Syed

  I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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• Difference between float and double

  - by VaioIsBorn

  I know, i've read about the difference between double precision and single precision etc. But they should give the same results on most cases right ? I was solving a problem on a programming contest and there were calculations with floating point numbers that were not really big so i decided to use float instead of double, and i checked it - i was getting the correct results. But when i send the solution, it said only 1 of 10 tests was correct. I checked again and again, until i found that using float is not the same using double. I put double for the calculations and double for the output, and the program gave the SAME results, but this time it passed all the 10 tests correctly. I repeat, the output was the SAME, the results were the SAME, but putting float didn't work - only double. The values were not so big too, and the program gave the same results on the same tests both with float and double, but the online judge accepted only the double-provided solution. Why ? What is the difference ?

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