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• Highlighting a custom UIButton

  - by Dan Ray

  The app I'm building has LOTS of custom UIButtons laying over top of fairly precisely laid out images. Buttonish, controllish images and labels and what have you, but with a clear custom-style UIButton sitting over top of it to handle the tap. My client yesterday says, "I want that to highlight when you tap it". Never mind that it immediately pushes on a new uinavigationcontroller view... it didn't blink, and so he's confused. Oy. Here's what I've done to address it. I don't like it, but it's what I've done: I subclassed UIButton (naming it FlashingUIButton). For some reason I couldn't just configure it with a background image on control mode highlighted. It never seemed to hit the state "highlighted". Don't know why that is. So instead I wrote: -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [self setBackgroundImage:[UIImage imageNamed:@"grey_screen"] forState:UIControlStateNormal]; [self performSelector:@selector(resetImage) withObject:nil afterDelay:0.2]; [super touchesBegan:touches withEvent:event]; } -(void)resetImage { [self setBackgroundImage:nil forState:UIControlStateNormal]; } This happily lays my grey_screen.png (a 30% opaque black box) over the button when it's tapped and replaces it with happy emptyness .2 of a second later. This is fine, but it means I have to go through all my many nibs and change all my buttons from UIButtons to FlashingUIButtons. Which isn't the end of the world, but I'd really hoped to address this as a UIButton category, and hit all birds with one stone. Any suggestions for a better approach than this one?

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• Letting user carry on after three attempts

  - by sMilbz

  In my spelling game there is a grid that is populated with words. The words are hidden and the aim of the game is to spell the word that is highlighted with the aid of a sound and a picture. To highlight a word you press the "next" button. At the moment if you spell the word correctly it says "well done" and you can advance to the next word, but if you spell it incorrectly you have to keep attempting the word until it is complete. As the game is designed for children I do not think this is the best approach, so I would like to make it so you can advance after 3 incorrect attempts. I have played around with the script so much trying to put counters on incorrect attempts and then making the button active but cannot seem to get it to work. Can someone please help me? Here is the script for the button var noExist = $('td[data-word=' + listOfWords[rndWord].name + ']').hasClass('wordglow2'); if (noExist) { $('.minibutton').click(); } else { $('.minibutton').click('disable'); $("#mysoundclip").attr('src', listOfWords[rndWord].audio); audio.play(); $("#mypic").attr('src', listOfWords[rndWord].pic); pic.show(); } }); "wordglow2" is the style applied if the word is spelt correctly. Here is a fiddle to help understand... http://jsfiddle.net/smilburn/ZAfVZ/4/

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• How do you chain functions dynamically in jQuery?

  - by clarke78

  I want to loop through an object that contains functions which will execute one after another. My most ideal approach would be to have these chain somehow (ie. func2 waits for func1 and func3 waits for func2) but this needs to happen dynamically and the functions will all have different durations. I'm using jQuery so I thought that perhaps "queue()" may help but I haven't worked with it much. A main concern is to not add any scope/callbacks to the functions within the object. I'd rather somehow enclose them within a parent function to execute within the loop in order to create the callback/chaining. Here's an example of what I've got now, but dumbed down. Thanks for any help! var obj = [ {'name':'func1','callback':function(){ alert(1); }}, {'name':'func2','callback':function(){ alert(2); }}, {'name':'func3','callback':function(){ alert(3); }} ]; $.each(obj, function(x, el) { el.callback(); });

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• F# insert/remove item from list

  - by Timothy

  How should I go about removing a given element from a list? As an example, say I have list ['A'; 'B'; 'C'; 'D'; 'E'] and want to remove the element at index 2 to produce the list ['A'; 'B'; 'D'; 'E']? I've already written the following code which accomplishes the task, but it seems rather inefficient to traverse the start of the list when I already know the index. let remove lst i = let rec remove lst lst' = match lst with | [] -> lst' | h::t -> if List.length lst = i then lst' @ t else remove t (lst' @ [h]) remove lst [] let myList = ['A'; 'B'; 'C'; 'D'; 'E'] let newList = remove myList 2 Alternatively, how should I insert an element at a given position? My code is similar to the above approach and most likely inefficient as well. let insert lst i x = let rec insert lst lst' = match lst with | [] -> lst' | h::t -> if List.length lst = i then lst' @ [x] @ lst else insert t (lst' @ [h]) insert lst [] let myList = ['A'; 'B'; 'D'; 'E'] let newList = insert myList 2 'C'

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• Use of Java [Interfaces / Abstract classes]

  - by Samuel

  Hello, Lately i decided to take a look at Java so i am still pretty new to it and also to the approach of OO programming, so i wanted to get some things straight before learning more, (i guess it's never to soon to start with good practices). I am programming a little 2D game for now but i think my question applies to any non trivial project. For the simplicity i'll provide examples from my game. I have different kinds of zombies, but they all have the same attributes (x, y, health, attack etc) so i wrote an interface Zombie which i implement by WalkingZombie, RunningZombie TeleportingZombie etc. Is this the best thing to do? Am i better of with an abstract class? Or with a super class? (I am not planning to partially implement functions - therefor my choice for an interface instead of an abstract class) I have one class describing the main character (Survivor) and since it is pretty big i wanted to write an interface with the different functions, so that i can easily see and share the structure of it. Is it good practice? Or is it simply a waste of space and time? I hope this question will not be rated as subjective because i thought that experienced programmers won't disagree about this kind of topic since the use of interfaces / super classes / abstract classes follows logical rules and is thereby not simply a personal choice. Thank you for your time -Samuel

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• How to structure code with 2 methods, one after another, which throw the same two exceptions?

  - by dotnetdev

  Hi, I have two methods, one called straight after another, which both throw the exact same 2 exceptions (IF an erroneous condition occurs, not stating that I'm getting exceptions). For this, should I write seperate try and catch blocks with the one statement in each try block and catch both exceptions (Both of which I can handle as I checked MSDN class library reference and there is something I can do, eg, re-open SqlConnection or run a query and not a stored proc which does not exist). So code like this: try { obj.Open(); } catch (SqlException) { // Take action here. } catch (InvalidOperationException) { // Take action here. } And likewise for the other method I call straight after. This seems like a very messy way of coding. The other way is to code with the exception variable (that is ommited as I am using AOP to log the exception details, using a class-level attribute). Doing this, this could aid me in finding out which method caused an exception and then taking action accordingly. Is this the best approach or is there another best practise altogether? I also assume that, as only these two methods are thrown, I do not need to catch Exception as that would be for an exception I cannot handle (causes way out of my control). Thanks

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• How do I choose what and when to cache data with ob_start rather than query the database?

  - by Tim Santeford

  I have a home page that has several independent dynamic parts. The parts consist of a list of recent news from the company, a site statistics panel, and the online status of certain employees. The recent news changes monthly, site statistics change daily, and online statuses change on a per minute bases. I would like to cache these panels so that the db is not hit on every page load. Is using ob_start() then ob_get_contents() to cache these parts to a file the correct way to do this or is there a better method in PHP5 for doing this? In asking this question I'm trying to answer these additional questions: How can I determine the correct approach for caching this data without doing extensive benchmarking? Does it make sense to cache these parts in different files and then join them together per requests or should I re-query the data and cache once per minute? I'm looking for a rule of thumb for planning pages and for situations where doing testing is not cost effective (The client is not paying enough for it I mean). Thanks!

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• Write out to text file using T-SQL

  - by sasfrog

  I am creating a basic data transfer task using TSQL where I am retrieving certain records from one database that are more recent than a given datetime value, and loading them into another database. This will happen periodically throughout the day. It's such a small task that SSIS seems like overkill - I want to just use a scheduled task which runs a .sql file. Where I need guidance is that I need to persist the datetime from the last run of this task, then use this to filter the records next time the task runs. My initial thought is to just store the datetime in a text file, and update (overwrite) it as part of the task each time it runs. I can read the file in without problems using T-SQL, but writing back out has got me stuck. I've seen plenty of examples which make use of a dynamically-built bcp command, which is then executed using xp_cmdshell. Trouble is, security on the server I'm deploying to precludes the use of xp_cmdshell. So, my question is, are there other ways to simply write a datetime value to a file using TSQL, or should I be thinking about a different approach? EDIT: happy to be corrected about SSIS being "overkill"...

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• Is there a Java data structure that is effectively an ArrayList with double indicies and built-in in

  - by Bob Cross

  I am looking for a pre-built Java data structure with the following characteristics: It should look something like an ArrayList but should allow indexing via double-precision rather than integers. Note that this means that it's likely that you'll see indicies that don't line up with the original data points (i.e., asking for the value that corresponds to key "1.5"). As a consequence, the value returned will likely be interpolated. For example, if the key is 1.5, the value returned could be the average of the value at key 1.0 and the value at key 2.0. The keys will be sorted but the values are not ensured to be monotonically increasing. In fact, there's no assurance that the first derivative of the values will be continuous (making it a poor fit for certain types of splines). Freely available code only, please. For clarity, I know how to write such a thing. In fact, we already have an implementation of this and some related data structures in legacy code that I want to replace due to some performance and coding issues. What I'm trying to avoid is spending a lot of time rolling my own solution when there might already be such a thing in the JDK, Apache Commons or another standard library. Frankly, that's exactly the approach that got this legacy code into the situation that it's in right now.... Is there such a thing out there in a freely available library?

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• Is a web-server (e.g servlets) a good solution for an IM server?

  - by John

  I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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• Why am I needing to click twice on a WPF listbox item in order to fire a command?

  - by Donal

  Hi, I'm trying to make a standard WPF listbox be dynamically filled, and for each item in the list box to launch a command when clicked. Currently I have a working listbox, which can be filled and each item will fire the correct command, but in order to fire the command I have to click the list item twice. i.e, Click once to select the item, then click on the actual text to fire the command. As the list is dynamically created, I had to create a data template for the list items: <ListBox.ItemTemplate> <DataTemplate> <TextBlock Margin="4,2,4,2"> <Hyperlink TextDecorations="None" Command="MyCommands:CommandsRegistry.OpenPanel"> <TextBlock Text="{Binding}" Margin="4,2,4,2"/> </Hyperlink> </TextBlock> </DataTemplate> </ListBox.ItemTemplate> Basically, how do I remove the need to click twice? I have tried to use event triggers to fire the click event on the hyperlink element when the list box item is selected, but I can't get it to work. Or, is there a better approach to dynamically fill a listbox and attach commands to each list item? Thanks

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• implementing interface

  - by 1ace1

  hello guys so i have this assignment that i need to implement interface to go over an ArrayList and sort it (ascending or descnding).I dont want "the" answer i just need some suggestions on my approach and why i get this error Exception in thread "main" java.lang.ClassCastException: Week7.Check cannot be cast to java.lang.Comparable at java.util.Arrays.mergeSort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at java.util.Collections.sort(Unknown Source) at Week7.TestCheck.main(TestCheck.java:18) This is how i did it: comparable had one method called public int compairTo(Object o) public class Check implements comparable { private Integer checkNumber; public Check(Integer newCheckNumber) { setCheckNumber(newCheckNumber); } public String toString() { return getCheckNumber().toString(); } public void setCheckNumber(Integer checkNumber) { this.checkNumber = checkNumber; } public Integer getCheckNumber() { return checkNumber; } @Override public int compairTo(Object o) { Check compair = (Check)o; int result = 0; if (this.getCheckNumber() > compair.getCheckNumber()) result = 1; else if(this.getCheckNumber() < compair.getCheckNumber()) result = -1; return result; } } in my main i had this import java.util.ArrayList; import java.util.Collections; public class TestCheck { public static void main(String[] args) { ArrayList checkList = new ArrayList(); checkList.add(new Check(445)); checkList.add(new Check(101)); checkList.add(new Check(110)); checkList.add(new Check(553)); checkList.add(new Check(123)); Collections.sort(checkList); for (int i =0; i < checkList.size(); i++){ System.out.println(checkList.get(i)); } } }

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• How to combine two rows and calculate the time difference between two timestamp values in MySQL?

  - by Nadar

  I have a situation that I'm sure is quite common and it's really bothering me that I can't figure out how to do it or what to search for to find a relevant example/solution. I'm relatively new to MySQL (have been using MSSQL and PostgreSQL earlier) and every approach I can think of is blocked by some feature lacking in MySQL. I have a "log" table that simply lists many different events with their timestamp (stored as datetime type). There's lots of data and columns in the table not relevant to this problem, so lets say we have a simple table like this: CREATE TABLE log ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(16), ts DATETIME NOT NULL, eventtype VARCHAR(25), PRIMARY KEY (id) ) Let's say that some rows have an eventtype = 'start' and others have an eventtype = 'stop'. What I want to do is to somehow couple each "startrow" with each "stoprow" and find the time difference between the two (and then sum the durations per each name, but that's not where the problem lies). Each "start" event should have a corresponding "stop" event occuring at some stage later then the "start" event, but because of problems/bugs/crashed with the data collector it could be that some are missing. In that case I would like to disregard the event without a "partner". That means that given the data: foo, 2010-06-10 19:45, start foo, 2010-06-10 19:47, start foo, 2010-06-10 20:13, stop ..I would like to just disregard the 19:45 start event and not just get two result rows both using the 20:13 stop event as the stop time. I've tried to join the table with itself in different ways, but the key problems for me seems to be to find a way to correctly identify the corresponding "stop" event to the "start" event for the given "name". The problem is exactly the same as you would have if you had table with employees stamping in and out of work and wanted to find out how much they actually were at work. I'm sure there must be well known solutions to this, but I can't seem to find them...

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• Optimize Duplicate Detection

  - by Dave Jarvis

  Background This is an optimization problem. Oracle Forms XML files have elements such as: <Trigger TriggerName="name" TriggerText="SELECT * FROM DUAL" ... /> Where the TriggerText is arbitrary SQL code. Each SQL statement has been extracted into uniquely named files such as: sql/module=DIAL_ACCESS+trigger=KEY-LISTVAL+filename=d_access.fmb.sql sql/module=REP_PAT_SEEN+trigger=KEY-LISTVAL+filename=rep_pat_seen.fmb.sql I wrote a script to generate a list of exact duplicates using a brute force approach. Problem There are 37,497 files to compare against each other; it takes 8 minutes to compare one file against all the others. Logically, if A = B and A = C, then there is no need to check if B = C. So the problem is: how do you eliminate the redundant comparisons? The script will complete in approximately 208 days. Script Source Code The comparison script is as follows: #!/bin/bash echo Loading directory ... for i in $(find sql/ -type f -name \*.sql); do echo Comparing $i ... for j in $(find sql/ -type f -name \*.sql); do if [ "$i" = "$j" ]; then continue; fi # Case insensitive compare, ignore spaces diff -IEbwBaq $i $j > /dev/null # 0 = no difference (i.e., duplicate code) if [ $? = 0 ]; then echo $i :: $j >> clones.txt fi done done Question How would you optimize the script so that checking for cloned code is a few orders of magnitude faster? System Constraints Using a quad-core CPU with an SSD; trying to avoid using cloud services if possible. The system is a Windows-based machine with Cygwin installed -- algorithms or solutions in other languages are welcome. Thank you!

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• Add Hover display for table cell

  - by Jake

  I have a table, but it is not in a list format, meaning not a column/row format. I look for specific cells to add a hover event that displays a description of the cell. $("#TableID td").hover(function(){ //ifCellThatIWant $(this).append("<span>Message that was brought in</span>"); }, function(){ $(this).children().remove(); }); The problem is right now is that the hover displays a span(with info. inside) that I used jquery to append the span to the cell when mouseover, which expands the cell, which is an effect that I don't like or want. I'm Trying to have an out of the table look,but still be by the cell that triggered the event; because if the span has a lot of info. in it, expanding the cell dynamically will start to look pretty nasty. Also will help if I had some type of css direction on how will I make the display for the mouseover "description" span look nice. My mind thought is that a way to accomplish what I want is giver the appended span the position of my mouse cursor when hover, but not sure if its the right approach or what the syntax would look like.

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• Is method reference caching a good idea in Java 8?

  - by gexicide

  Consider I have code like the following: class Foo { Y func(X x) {...} void doSomethingWithAFunc(Function<X,Y> f){...} void hotFunction(){ doSomethingWithAFunc(this::func); } } Consider that hotFunction is called very often. Would it then be advisable to cache this::func, maybe like this: class Foo { Function<X,Y> f = this::func; ... void hotFunction(){ doSomethingWithAFunc(f); } } As far as my understanding of java method references goes, the Virtual Machine creates an object of an anonymous class when a method reference is used. Thus, caching the reference would create that object only once while the first approach creates it on each function call. Is this correct? Should method references that appear at hot positions in the code be cached or is the VM able to optimize this and make the caching superfluous? Is there a general best practice about this or is this highly VM-implemenation specific whether such caching is of any use?

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• How can I [simply] consume JSON Data in a Line of Business Web Application

  - by Atomiton

  I usually use JSON with jQuery to just return a string with html. However, I want to start to use Javascript objects in my code. What's the simplest way to get started using json objects on my page? Here's a sample Ajax call ( after $(document).ready( { ... }) of course: $('#btn').click(function(event) { event.preventDefault(); var out = $('#result'); $.ajax({ url: "CustomerServices.asmx/GetCustomersByInvoiceCount", success: function(msg) { // // Iterate through the json results and spit them out to a page? // }, data: "{ 'invoiceCount' : 100 }" }); }); My WebMethod: [WebMethod(Description="Gets customers with more than n invoices")] public List<Customer> GetCustomersByInvoiceCount(int? invoiceCount) { using (dbDataContext db = new dbDataContext()) { return db.Customers.Where(c => c.InvoiceCount >= invoiceCount); } } What gets returned: {"d":[{"__type":"Customer","Account":"1116317","Name":"SOME COMPANY","Address":"UNit 1 , 392 JOHN ST. ","LastTransaction":"\/Date(1268294400000)\/","HighestBalance":13922.34},{"__type":"Customer","Account":"1116318","Name":"ANOTHER COMPANY","Address":"UNIT #345 , 392 JOHN ST. ","LastTransaction":"\/Date(1265097600000)\/","HighestBalance":549.42}]} What I'd LIKE to know, is what are people generally doing with this returned json? Do you iterate through the properties and create an html table on the fly? Is there way to "bind" JSON data using a javascript version of reflection ( something like the .Net GridView Control ) Do you throw this returned data into a Javascript Object and then do something with it? An example of what I want to achieve is to have an plain ol' html page ( on a mobile device )with a list of a Salesperson's Customers. When one of those customers are clicked, the customer id gets sent to a webservice which retrieves the customer details that are relevant to a sales person. I know the SO talent pool is quite deep so I figured you all here would be able to guide in the right direction and give me a few ideas on the best way to approach this.

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• VB6 Game Development : Don't ask me why :-)

  - by CVS-2600Hertz-wordpress-com

  Hi All, I am developing a game in VB6 (plz don't ask me why :) ). The storyboard is ready and a rough implementation is underway. I am following a "pure-software-rendering" approach. (i.e. no DirectX, no openGL etc.) Amongst many others, the following "serious" problems exist: 2D alpha transparency reqd. to implement overlays. Parallax implementation to give depth-of-field illusion. Capturing mouse-scroll events globally (as in FPS-es; mapping them to changing weapon). Async sound play with absolute "zero-lag". Any ideas anyone. Please suggest any well documented library/ocx or sample-code. Plz do provide solutions with max performance and with as little overhead as possible. Also, anyone who has developed any games, and would be open to sharing her/his code would be highly appreciated. (any well-acknowledged VB games whose source-code i can study??) Thank You

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• iPhone application purchase verification -- possible?

  - by Sedate Alien

  The iPhone 3.0 SDK's StoreKit.framework provides support for in-app purchases to give the user additional content, functionality and so on. It is possible for an app to send the transactionReceipt property of SKPaymentTransaction objects to the developer's server for verification of successful purchasing before granting service. Is there any analogous SDK to verify the initial application purchase itself? A developer that wishes for their server to only provide services to genuine applications (i.e. not pirated) without using IAP could do so by verifying the application in this manner, e.g. ensure that only users with the correct transactionReceipt are catered for. I understand that this approach would still be vulnerable to replay attacks; a dedicated group of pirates could share a valid transactionReceipt. However, my server provides a consumable service to users, i.e. once they've connected and done the work, it needn't work a second time so replay attacks are nullified. The service that my app provides is relatively niche. I could distribute it on the App Store as a free application that requires at least one IAP to do anything useful, but I am lead to believe that this would be a very unpopular move among users as it would be considered misleading. If I distribute it as a paid app, I do not know how to ensure that only genuine apps can access the webservice. This is important as every invocation of the webservice costs me money! What are my options?

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• How to write a generic USB Host Driver for Printers from various vendors?

  - by Ullas

  I want to develop a USB host on an embedded device that will talk to printers from various vendors. Drivers for the vendor specific printers would be available on PC which is ultimately communicating with printer but my device is facilitating this communication and needs to perform the basic handshaking/setup of the printer (i.e, it needs to know when the printer is connected, what are the socket IDs that needs to be opened for CTRL and DATA transmissions etc). All of these printers are supposed to comply with IEEE 1284.4 standards but I see that many of them vary quiet a bit. One approach I have is to take the USB traces of handshaking from each of these printers and write various sections of code respectively (I know, that sounds ridiculous!). Is there a generic way to do this? Is there any available forum where these standard informations are mentioned? For eg: EPSON uses 'EPSON-CTRL' and 'EPSON-DATA' for its control and data services which needs to be provided to get the socket ID for these services. I am pretty sure HPs, Canon's etc would have their own service names as well. As per the standards, this was supposed to be captured in IANA but I dont see anything there. Any help on this would be greatly appreciated. Thanks and regards, Ullas

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• Java iterative vs recursive

  - by user1389813

  Can anyone explain why the following recursive method is faster than the iterative one (Both are doing it string concatenation) ? Isn't the iterative approach suppose to beat up the recursive one ? plus each recursive call adds a new layer on top of the stack which can be very space inefficient. private static void string_concat(StringBuilder sb, int count){ if(count >= 9999) return; string_concat(sb.append(count), count+1); } public static void main(String [] arg){ long s = System.currentTimeMillis(); StringBuilder sb = new StringBuilder(); for(int i = 0; i < 9999; i++){ sb.append(i); } System.out.println(System.currentTimeMillis()-s); s = System.currentTimeMillis(); string_concat(new StringBuilder(),0); System.out.println(System.currentTimeMillis()-s); } I ran the program multiple time, and the recursive one always ends up 3-4 times faster than the iterative one. What could be the main reason there that is causing the iterative one slower ?

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• Casting/dereferencing member variable pointer from void*, is this safe?

  - by Damien

  Hi all, I had a problem while hacking a bigger project so I made a simpel test case. If I'm not omitting something, my test code works fine, but maybe it works accidentally so I wanted to show it to you and ask if there are any pitfalls in this approach. I have an OutObj which has a member variable (pointer) InObj. InObj has a member function. I send the address of this member variable object (InObj) to a callback function as void*. The type of this object never changes so inside the callback I recast to its original type and call the aFunc member function in it. In this exampel it works as expected, but in the project I'm working on it doesn't. So I might be omitting something or maybe there is a pitfall here and this works accidentally. Any comments? Thanks a lot in advance. (The problem I have in my original code is that InObj.data is garbage). #include <stdio.h> class InObj { public: int data; InObj(int argData); void aFunc() { printf("Inside aFunc! data is: %d\n", data); }; }; InObj::InObj(int argData) { data = argData; } class OutObj { public: InObj* objPtr; OutObj(int data); ~OutObj(); }; OutObj::OutObj(int data) { objPtr = new InObj(data); } OutObj::~OutObj() { delete objPtr; } void callback(void* context) { ((InObj*)context)->aFunc(); } int main () { OutObj a(42); callback((void*)a.objPtr); }

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• How to find sum of node's value for given depth in binary tree?

  - by masato-san

  I've been scratching my head for several hours for this... problem: Binary Tree (0) depth 0 / \ 10 20 depth 1 / \ / \ 30 40 50 60 depth 2 I am trying to write a function that takes depth as argument and return the sum of values of nodes of the given depth. For instance, if I pass 2, it should return 180 (i.e. 30+40+50+60) I decided to use breath first search and when I find the node with desired depth, sum up the value, but I just can't figure out how to find out the way which node is in what depth. But with this approach I feel like going to totally wrong direction. function level_order($root, $targetDepth) { $q = new Queue(); $q->enqueue($root); while(!$q->isEmpty) { //how to determin the depth of the node??? $node = $q->dequeue(); if($currentDepth == $targetDepth) { $sum = $node->value; } if($node->left != null) { $q->enqueue($node->left); } if($node->right != null) { $q->enqueue($node->right); } //need to reset this somehow $currentDepth ++; } }

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• How to make 2 incompatible types, but with the same members, interchangeable?

  - by Quigrim

  Yesterday 2 of the guys on our team came to me with an uncommon problem. We are using a third-party component in one of our winforms applications. All the code has already been written against it. They then wanted to incorporate another third-party component, by the same vender, into our application. To their delight they found that the second component had the exact same public members as the first. But to their dismay, the 2 components have completely separate inheritance hierarchies, and implement no common interfaces. Makes you wonder... Well, makes me wonder. An example of the problem: public class ThirdPartyClass1 { public string Name { get { return "ThirdPartyClass1"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass1 is doing its thing."); } } public class ThirdPartyClass2 { public string Name { get { return "ThirdPartyClass2"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass2 is doing its thing."); } } Gladly they felt copying and pasting the code they wrote for the first component was not the correct answer. So they were thinking of assigning the component instant into an object reference and then modifying the code to do conditional casts after checking what type it was. But that is arguably even uglier than the copy and paste approach. So they then asked me if I can write some reflection code to access the properties and call the methods off the two different object types since we know what they are, and they are exactly the same. But my first thought was that there goes the elegance. I figure there has to be a better, graceful solution to this problem.

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• How to check if a thread is busy in C#?

  - by Sam

  I have a Windows Forms UI running on a thread, Thread1. I have another thread, Thread2, that gets tons of data via external events that needs to update the Windows UI. (It actually updates multiple UI threads.) I have a third thread, Thread3, that I use as a buffer thread between Thread1 and Thread2 so that Thread2 can continue to update other threads (via the same method). My buffer thread, Thread3, looks like this: public class ThreadBuffer { public ThreadBuffer(frmUI form, CustomArgs e) { form.Invoke((MethodInvoker)delegate { form.UpdateUI(e); }); } } What I would like to do is for my ThreadBuffer to check whether my form is currently busy doing previous updates. If it is, I'd like for it to wait until it frees up and then invoke the UpdateUI(e). I was thinking about either: a) //PseudoCode while(form==busy) { // Do nothing; } form.Invoke((MethodInvoker)delegate { form.UpdateUI(e); }); How would I check the form==busy? Also, I am not sure that this is a good approach. b) Create an event in form1 that will notify the ThreadBuffer that it is ready to process. // psuedocode List<CustomArgs> elist = new List<CustomArgs>(); public ThreadBuffer(frmUI form, CustomArgs e) { from.OnFreedUp += from_OnFreedUp(); elist.Add(e); } private form_OnFreedUp() { if (elist.count == 0) return; form.Invoke((MethodInvoker)delegate { form.UpdateUI(elist[0]); }); elist.Remove(elist[0]); } In this case, how would I write an event that will notify that the form is free? and c) an other ideas?

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