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• multiple clients - one server connection with sockets tcp/ip c# .net

  - by jagse

  Hello guys, I need to develop a client server system where I can have multiple clients communicating with one server at the same time. I want to communicate xml serialized objects and also need to send and receive other commands to invoke methods. Now, I am just starting with socket programming in C# and .Net and found that the asynchronous I/O is the way to go so that the methods dont block the execution of code. Also there are many examples of how to make a simple client server system. So I have a basic understanding of how that works. Anyway, what still is not clear to me is how I can set up a server which can manage connections to multiple clients? Can I just create a new socket per connection and then store those in some kind of list? Do I need some kind of multiplexing to achieve this? Do I have to listen at multiple ports? What`s the best way here? And the other thing is if I need to develop my own protocol to differentiate between what I am actually sending over the network -- xml serialized object or a command which might be just a string encoded in ascII or something. Or would I develop my own protocol just to send these commands? Any kind of help is apreciated! If someone knows a good book which covers this sort of stuff, let me know. Cheers I forgot to mention that some of my clients which are supposed to communicate with my server will be pda and I therefore use the compact framework... So this might bring in some restrictions...

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• What are the differences between mapping,binding and parsing?

  - by sfrj

  I am starting to learn web-services in java EE6. I did web development before, but never nothing related to web services. All is new to me and the books and the tutorials i find in the web are to technical. I started learning about .xsd schemas and also .xml. In that topic i feel confident, i understand what are the schemas used for and what validation means. Now my next step is learning about JAX-B(Java Api for XML Binding). I rode some about it and i did also some practice in my IDE. But i have lots of basic doubts, that make me stuck and cannot feel confident to continue to the next topic. Ill appreciate a lot if someone could explain me well my doubts: What does it mean mapping and what is a mapping tool? What does it mean binding and what is a binding tool? What does it mean parsing and what is a parsing tool? How is JAX-B related to mapping,binding and parsing? I am seeking for a good answer built by you, not just a copy paste from google(Ive already been online a few hours and only got confused).

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• Why doesn't the Java Collections API include a Graph implementation?

  - by dvanaria

  I’m currently learning the Java Collections API and feel I have a good understanding of the basics, but I’ve never understood why this standard API doesn’t include a Graph implementation. The three base classes are easily understandable (List, Set, and Map) and all their implementations in the API are mostly straightforward and consistent. Considering how often graphs come up as a potential way to model a given problem, this just doesn’t make sense to me (it’s possible it does exist in the API and I’m not looking in the right place of course). Steve Yegge suggests in one of his blog posts that a programmer should consider graphs first when attacking a problem, and if the problem domain doesn’t fit naturally into this data structure, only then consider the alternative structures. My first guess is that there is no universal way to represent graphs, or that their interfaces may not be generic enough for an API implementation to be useful? But if you strip down a graph to its basic components (vertices and a set of edges that connect some or all of the vertices) and consider the ways that graphs are commonly constructed (methods like addVertex(v) and insertEdge(v1, v2)) it seems that a generic Graph implementation would be possible and useful. Thanks for helping me understand this better.

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• how to put header authentication into a form using php?

  - by SkyWookie

  Hey guys, for the page I am doing needs a login authentication using Twitter (using tweetphp API). For test purposes I used this code below to do a successful login: if (!isset($_SERVER['PHP_AUTH_USER'])){ header('WWW-Authenticate: Basic realm="Enter your Twitter username and password:"'); header('HTTP/1.0 401 Unauthorized'); echo 'Please enter your Twitter username and password to view your followers.'; exit(); } $username = $_SERVER['PHP_AUTH_USER']; $password = $_SERVER['PHP_AUTH_PW']; The problem now is, I want to integrate it into a form, so far I have the following: <form action="logincheck.php" method="post" class="niceform" > <fieldset> <legend>Twitter Login:</legend> <dl> <dt><label for="email">Twitter Username:</label></dt> <dd><input type="text" name="username" id="username" size="32" maxlength="128" /></dd> </dl> <dl> <dt><label for="password">Password:</label></dt> <dd><input type="password" name="password" id="password" size="32" maxlength="32" /></dd> </dl> </fieldset> <fieldset class="action"> <input type="submit" name="submit" id="submit" value="Submit" /> I am sending it to logincheck.php, this is where I think I get stuck. I am not sure how to compare the form data with Twitter's login data. I was trying a similar if statement as I used in the first code (box that pops up before page loads), but I couldn't wrap my head around it. Thanks again guys!

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• What's an effective way to move data from one open browser tab to another?

  - by slk

  I am looking for a quick way to grab some data off of one Web page and throw it into another. I don't have access to the query string in the URL of the second page, so passing the data that way is not an option. Right now, I am using a Greasemonkey user script in tandem with a JS bookmarklet trigger: javascript:doIt(); // ==UserScript== // @include public_site // @include internal_site // ==/UserScript== if (document.location.host.match(internal_site)) { var datum1 = GM_getValue("d1"); var datum2 = GM_getValue("d2"); } unsafeWindow.doIt = function() { if(document.location.host.match(public_site)) { var d1 = innerHTML of page element 1; var d2 = innerHTML of page element 2; //Next two lines use setTimeout to bypass GM_setValue restriction window.setTimeout(function() {GM_setValue("d1", d1);}, 0); window.setTimeout(function() {GM_setValue("d2", d2);}, 0); } else if(document.location.host.match(internal_site)) { document.getElementById("field1").value = datum1; document.getElementById("field2").value = datum2; } } While I am open to another method, I would prefer to stay with this basic model if possible, as this is just a small fraction of the code in doIt() which is used on several other pages, mostly to automate date-based form fills; people really like their "magic button." The above code works, but there's an interruption to the workflow: In order for the user to know which page on the public site to grab data from, the internal page has to be opened first. Then, once the GM cookie is set from the public page, the internal page has to be reloaded to get the proper information into the internal page variables. I'm wondering if there's any way to GM_getValue() at bookmarklet-clicktime to prevent the need for a refresh. Thanks!

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• Program structure in long running data processing python script

  - by fmark

  For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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• Effective books for learning the intricacies of business application development?

  - by OffApps Cory

  I am a self taught "developer". I use the term loosely because I only know enough to make myself dangerous. I have no theory background, and I only pick up things to get this little tool to work or make that control do what I want. That said, I am looking for some reading material that explains some of the theory behind application development especially from a business standpoint. Really I need to understand what all of these terms that float around really talk about. Business Logic Layer, UI abstraction level and all that. Anyone got a reading list that they feel helped them understand this stuff? I know how to code stuff up so that it works. It is not pretty mostly because I don't know the elegant way of doing it, and it is not planned out very well (I also don't know how to plan an application). Any help would be appreciated. I have read a number of books on what I thought was the subject, but they all seem to rehash basic coding and what-not. This doesn't have to be specific to VB.NET or WPF (or Entity Framework) but anything with those items would be quite helpful.

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• how to allow unamed user in svn authz file?

  - by dtrosset

  I have a subversion server running with apache. It authenticates users using LDAP in apache configuration and uses SVN authorizations to limit user access to certain repositories. This works perfectly. Apache DAV svn SVNParentPath /srv/svn SVNListParentPath Off SVNPathAuthz Off AuthType Basic AuthName "Subversion Repository" AuthBasicProvider ldap AuthLDAPBindDN # private stuff AuthLDAPBindPassword # private stuff AuthLDAPURL # private stuff Require valid-user AuthzSVNAccessFile /etc/apache2/dav_svn.authz Subversion [groups] soft = me, and, all, other, developpers Adding anonymous access from one machine Now, I have a service I want to setup (rietveld, for code reviews) that needs to have an anonymous access to the repository. As this is a web service, accesses are always done from the same server. Thus I added apache configuration to allow all accesses from this machine. This did not work until I add an additional line in the authorization file to allow read access to user -. Apache <Limit GET PROPFIND OPTIONS REPORT> Order allow,deny Allow from # private IP address Satisfy Any </Limit> Subversion [Software:/] @soft = rw - = r # <-- This is the added line For instance, before I add this, all users were authenticated, and thus had a name. Now, some accesses are done without a user name! I found this - user name in the apache log files. But does this line equals to * = r that I absolutely do not want to enable, or does it only allows the anonymous unnamed user (that is allowed access only from the rietveld server)?

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• How do I create rows with alternating colors for a UITableView on iPhone?

  - by Mat

  Hi all, i would to have alternate 2 colors of rows, like the first black, the second white, the third black, etc, etc... my approach is like a basic exercise of programming to calculate if a number is odd number or not: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; cell = ((MainCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]); if (cell==nil) { NSArray *topLevelObjects=[[NSBundle mainBundle] loadNibNamed:@"MainCell" owner:self options:nil]; for (id currentObject in topLevelObjects){ if ([currentObject isKindOfClass:[UITableViewCell class]]){ if ((indexPath.row % 2)==0) { [cell.contentView setBackgroundColor:[UIColor purpleColor]]; }else{ [cell.contentView setBackgroundColor:[UIColor whiteColor]]; } cell = (MainCell *) currentObject; break; } } }else { AsyncImageView* oldImage = (AsyncImageView*) [cell.contentView viewWithTag:999]; [oldImage removeFromSuperview]; }return cell; The problem is that when i do a rapid scroll, the background of cells become like the last 2 cell black, the first 2 cell white or something like this, but if i scroll slow works fine. I think the problem is the cache of reusableCell. Any ideas? TIA

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• How can I format Custom Data and display in autocomplete when source is an DB

  - by Andres Scarpone

  so I'm trying to get some info in the auto-complete widget like it's shown in the JQuery UI demo Demo, the only problem is they use a variable that they fill with the data they want to show, I instead want to access the data and the different description and stuff using a Data Base in MySQL, for this I have changed the source to use another php page that looks up the info. here is the code for the Auto-complete, I really don't understand the methods so I haven't changed it from the basic search. This is the JS: $(document).ready((function(){ $( "#completa" ).autocomplete({ source: "buscar.php", minLength: 1, focus: function (event, ui){ $("#completa").val(ui.item.val); return false; }; })); This is what I have in buscar.php: <?php $conec = mysql_connect(localhost, root, admin); if(!$conec) { die(mysql_error()); } else { $bd = mysql_select_db("ve_test",$conec ); if(!$bd) { die(mysql_error()); } } $termino = trim(strip_tags($_GET['term']));//Obtener el termino que envia el autocompletar $qstring = "SELECT name, descripcion FROM VE_table WHERE name LIKE '%".$termino."%'"; $result = mysql_query($qstring);//Solicitud a la Base de Datos while ($row = mysql_fetch_array($result,MYSQL_ASSOC))//Realizar un LOOP sobre los valores obtenidos { $row['value']=htmlentities(stripslashes($row['name'])); $row_set[] = $row;//build an array } echo json_encode($row_set);//Enviar los datos al autocompletar en codificacion JSON, Altamente Necesario. ?

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• Keeping cached browser data inside ASP update panel textboxes/dropdowns for browser back click

  - by pmlevere

  I'm new in VB.net/asp and am running a VB web application in a visual database program called IronSpeed designer. I'm primarily using IronSpeed in this case for its login/role security features. I have a basic two page setup for this app. The user logs in then is taken to AccountEntry.aspx, they enter data into textboxes and select some dropdown values that are linked to a sql database, then they click "submit" to move to Results.aspx. On Results.aspx, the user can change data and then generate several types of reports (PDF, Excel, etc). I'm used to setting up ASP controls inside ASPContent areas, and in these areas if a user performs a browser back click the previously entered data will still be on the page for potential user modification. However in this web app, IronSpeed is setting up the page and asp controls inside an asp update panel. It appears inside an asp update panel, cached values can't be seen on a browser back click. In this case, it's important that the orginally entered values still be there for the user experience if the user advances to Results.aspx then clicks browser back to modify a value on AccountEntry.aspx. If I have to I'll setup Session Variables and disable browser clicking, but that is last resort. Is there any way to save cached data inside an asp update panel and have it there for a browser back click?

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• strcmp() but with 0-9 AFTER A-Z? (C/C++)

  - by Aaron

  For reasons I completely disagree with but "The Powers (of Anti-Usability) That Be" continue to decree despite my objections, I have a sorting routine which does basic strcmp() compares to sort by its name. It works great; it's hard to get that one wrong. However, at the 11th hour, it's been decided that entries which begin with a number should come AFTER entries which begin with a letter, contrary to the ASCII ordering. They cite the EBCDIC standard has numbers following letters so the prior assumption isn't a universal truth, and I have no power to win this argument... but I digress. Therein lies my problem. I've replaced all appropriate references to strcmp with a new function call nonstd_strcmp, and now need to implement the modifications to accomplish the sort change. I've used a FreeBSD source as my base: http://freebsd.active-venture.com/FreeBSD-srctree/newsrc/libkern/strncmp.c.html if (n == 0) return (0); do { if (*s1 != *s2++) return (*(const unsigned char *)s1 - *(const unsigned char *)(s2 - 1)); if (*s1++ == 0) break; } while (--n != 0); return (0); I guess I might need to take some time away to really think about how it should be done, but I'm sure I'm not the only one who's experienced the brain-deadness of just-before-release spec changes.

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• Read/Write/Find/Replace huge csv file

  - by notapipe

  I have a huge (4,5 GB) csv file.. I need to perform basic cut and paste, replace operations for some columns.. the data is pretty well organized.. the only problem is I cannot play with it with Excel because of the size (2000 rows, 550000 columns). here is some part of the data: ID,Affection,Sex,DRB1_1,DRB1_2,SENum,SEStatus,AntiCCP,RFUW,rs3094315,rs12562034,rs3934834,rs9442372,rs3737728 D0024949,0,F,0101,0401,SS,yes,?,?,A_A,A_A,G_G,G_G D0024302,0,F,0101,7,SN,yes,?,?,A_A,G_G,A_G,?_? D0023151,0,F,0101,11,SN,yes,?,?,A_A,G_G,G_G,G_G I need to remove 4th, 5th, 6th, 7th, 8th and 9th columns; I need to find every _ character from column 10 onwards and replace it with a space ( ) character; I need to replace every ? with zero (0); I need to replace every comma with a tab; I need to remove first row (that has column names; I need to replace every 0 with 1, every 1 with 2 and every ? with 0 in 2nd column; I need to replace F with 2, M with 1 and ? with 0 in 3rd column; so that in the resulting file the output reads: D0024949 1 2 A A A A G G G G D0024302 1 2 A A G G A G 0 0 D0023151 1 2 A A G G G G G G (both input and output should read one line per row, ne extra blank row) Is there a memory efficient way of doing that with java(and I need a code to do that) or a usable tool for playing with this large data so that I can easily apply Excel functionality..

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• OpenSocial create activity from submit click

  - by russp

  Hi I'm "playing with OpsnSocial" and think I get a lot of it (well thanks to Googles' bits) but one question if I may. Creating an activity Lets say I have a form like this (simple) <form> <input type="text" name="" id="testinput" value=""/> <input type="submit" name="" id="" value=""/> </form> And I want to post the value of the text field (and or a message i.e "just posted" to the "users" activity. Do I use a function like this? function createActivity() { if (viewer) { var activity = opensocial.newActivity({ title: viewer.getDisplayName() + ' VALUE FROM FORM '}); opensocial.requestCreateActivity(activity, "HIGH", function() { setTimeout(initAllData,1000); }); } }; If so, how do I pass the text field value to it - is it something like this? var testinput = document.getElementById("testinput"); so the function may look like function createActivity() { if (viewer) { var activity = opensocial.newActivity({ title: viewer.getDisplayName() + testinput }); opensocial.requestCreateActivity(activity, "HIGH", function() { setTimeout(initAllData,1000); }); } }; And how do I trigger the function by using the submit button. In my basic JQuery I would use $('#submitID').submit(function(){ 'bits in here '}); Is at "simple as that i.e. use the createActivity function and it will use the OS framework to "post" to the activity.xml

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• Referencing not-yet-defined variables - Java

  - by user2537337

  Because I'm tired of solving math problems, I decided to try something more engaging with my very rusty (and even without the rust, very basic) Java skills. I landed on a super-simple people simulator, and thus far have been having a grand time working through the various steps of getting it to function. Currently, it generates an array of people-class objects and runs a for loop to cycle through a set of actions that alter the relationships between them, which I have stored in a 2d integer array. When it ends, I go look at how much they all hate each other. Fun stuff. Trouble has arisen, however, because I would like the program to clearly print what action is happening when it happens. I thought the best way to do this would be to add a string, description, to my "action" class (which stores variables for the actor, reactor, and the amount the relationship changes). This works to a degree, in that I can print a generic message ("A fight has occurred!") with no problem. However, ideally I would like it to be a little more specific ("Person A has thrown a rock at Person B's head!"). This latter goal is proving more difficult: attempting to construct an action with a description string that references actor and reactor gets me a big old error, "Cannot reference field before it is defined." Which makes perfect sense. I believe I'm not quite in programmer mode, because the only other way I can think to do this is an unwieldy switch statement that negates the need for each action to have its own nicely-packaged description. And there must be a neater way. I am not looking for examples of code, only a push in the direction of the right concept to handle this.

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• Why Does My Vector<PEVENTLOGRECORD> Mysteriously Get Cleared?

  - by Eric

  Hello everyone, I am making a program that reads and stores data from Windows EventLog files (.evt) in C++. I am using the calls OpenBackupEventLog(ServerName, FileName) and ReadEventLog(...). Also using this: PEVENTLOGRECORD Anyway, without supplying all of the code, here is the basic idea: 1. I get a handle to the .evt file using OpenBackupEventLog() and passing in a file name. 2. I then use ReadEventLog() to fill up a buffer with an unknown number of EventLog messages. 3. I traverse through the buffer and add each message to a vector 4. I keep filling up buffers (repeat steps 2 and 3) until I reach the end of the file. Here is my code for filling the vector: vector<PEVENTLOGRECORD> allRecords; while(_status == ERROR_SUCCESS) { if(!ReadEventLog(...)) CheckStatus(); else FillVectorFromBuffer(allRecords) } // Function FillVectorFromBuffer FillVectorFromBuffer(vector(PEVENTLOGRECORD) &allRecords) { int bytesExamined = 0; PBYTE pRecord = (PBYTE)_lpBuffer; // This is one of the params in ReadEventLog() while(bytesExamined < _pnBytesRead) // Another param from ReadEventLog { PEVENTLOGRECORD currentRecord = (PEVENTLOGRECORD)(pRecord); allRecords.push_back(currentRecord); pRecord += currentRecord->Length; bytesExamined += currentRecord->Length; } } Anyway, whenever I run this, it will get all the EventLogs in the file, and the vector will have everything I want it to. But as soon as this line: if(!ReadEventLog()) gets called and returns true (aka ReadEventLog() returns false), then every field in my vector gets set to zero. The vector will still contain the correct number of elements, it's just that all of the fields in the PEVENTLOGRECORD struct are now zero. Anyone with better debugging experience have any ideas? Thanks.

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• Good way to identify similar images?

  - by Nick

  I've developed a simple and fast algorithm in PHP to compare images for similarity. Its fast (~40 per second for 800x600 images) to hash and a unoptimised search algorithm can go through 3,000 images in 22 mins comparing each one against the others (3/sec). The basic overview is you get a image, rescale it to 8x8 and then convert those pixels for HSV. The Hue, Saturation and Value are then truncated to 4 bits and it becomes one big hex string. Comparing images basically walks along two strings, and then adds the differences it finds. If the total number is below 64 then its the same image. Different images are usually around 600 - 800. Below 20 and extremely similar. Are there any improvements upon this model I can use? I havent looked at how relevant the different components (hue, saturation and value) are to the comparison. Hue is probably quite important but the others? To speed up searches I could probably split the 4 bits from each part in half, and put the most significant bits first so if they fail the check then the lsb doesnt need to be checked at all. I dont know a efficient way to store bits like that yet still allow them to be searched and compared easily. I've been using a dataset of 3,000 photos (mostly unique) and there havent been any false positives. Its completely immune to resizes and fairly resistant to brightness and contrast changes.

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• getSharedPreferences not working for me with concerns to ListPreferences and Integers

  - by ideagent

  I'm stuck at a point where I'm trying to get my project to read a preference value (from a ListPreference listing) and then use that value in a basic mathematical subtraction instance. The problem is that the "seek" preference is not being seen by my Java code, and yet the default value is (I've tried the default value with 3000 and now 0). Am i missing something, is there a bug here, known or unknown? Java code chunk where the issues manifests itself: public static final String PREF_FILE_NAME = "preferences"; seekback.setOnClickListener(new Button.OnClickListener() { @Override public void onClick(View view) { try { SharedPreferences preferences = getSharedPreferences(PREF_FILE_NAME, MODE_PRIVATE); Integer storedPreference = preferences.getInt("seek", 0); (mediaPlayer.getCurrentPosition()-storedPreference); } catch (Exception e) { e.printStackTrace(); } } }); Here are some other code bits for my project: From preferences file: <ListPreference android:entries="@array/seconds" android:entryValues="@array/seconds_values" android:summary="sets the seek interval for the seekback and seekforward buttons" android:title="Seek Interval" android:defaultValue="5000" android:key="@string/seek" From strings file: seek From an array file: Five seconds Fifteen seconds Thirty seconds Sixty seconds 5000 15000 30000 60000 let me know if you need to see more code to figure this one out Thanks in advance for any help that can be offered. I've worked over this issue now for a few hours and I'm burnt, a second pair of eyes on it would be very much appreciated. Arg, not sure how to get the code and plain text to format nicely here, even tried the options, like Code Sample, no luck AndroidCoder

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• What file format can I use to output a formatted text file straight from a program without having the markup be too complicated?

  - by Matt

  Premise: I am parsing a file that is quite nearly XML, but not quite. From this file I would like to extract data and output in a file that a user could open up in some program and read. To make the data reasonable, I would almost certainly need to format the text. In case it matters, I will probably be using Java to write the program. Problem: I cannot find a file format that supports formatting without having terribly complex rules and encoding problems. Attempts: I looked into a basic .txt extension first, but it does not have enough formatting advantage. I then tried a .rtf extension, but the rules for outputting text seem to be terribly complicated. It was then suggested that I used XML, but I do not understand how this file would be viewed. This appears to be probably the best solution, but I don't understand much about it. Perhaps somebody could shed some light here. In Other Words: Could somebody suggest and easy to use file format and/or shed some light on how to use XML for text formatting and viewing?

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• Run Javascript on the body of a Gmail message

  - by saturn

  I want to display LaTeX math in the gmail messages that I receive, so that for example $\mathbb P^2$ would show as a nice formula. Now, there are several Javascripts available (for example, this one, or MathJax which would do the job, I just need to call them at the right time to manipulate the gmail message. I know that this is possible to do in "basic HTML" and "print" views. Is it possible to do in the standard Gmail view? I tried to insert a call to the javascript right before the "canvas_frame" iframe, but that did not work. My suspicion is that manipulating a Gmail message by any Javascript would be a major security flaw (think of all the malicious links one could insert) and that Google does everything to prevent this. And so the answer to my question is probably 'no'. Am I right in this? Of course, it would be very easy for Google to implement viewing of LaTeX and MathML math simply by using MathJax on their servers. I made the corresponding Gmail Lab request, but no answer, and no interest from Google apparently. So, again: is this possible to do without Google's cooperation, on the client side?

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• Program to find the result of primitive recursive functions

  - by alphomega

  I'm writing a program to solve the result of primitive recursive functions: 1 --Basic functions------------------------------ 2 3 --Zero function 4 z :: Int -> Int 5 z = \_ -> 0 6 7 --Successor function 8 s :: Int -> Int 9 s = \x -> (x + 1) 10 11 --Identity/Projection function generator 12 idnm :: Int -> Int -> ([Int] -> Int) 13 idnm n m = \(x:xs) -> ((x:xs) !! (m-1)) 14 15 --Constructors-------------------------------- 16 17 --Composition constructor 18 cn :: ([Int] -> Int) -> [([Int] -> Int)] -> ([Int] -> Int) 19 cn f [] = \(x:xs) -> f 20 cn f (g:gs) = \(x:xs) -> (cn (f (g (x:xs))) gs) these functions and constructors are defined here: http://en.wikipedia.org/wiki/Primitive_recursive_function The issue is with my attempt to create the compositon constructor, cn. When it gets to the base case, f is no longer a partial application, but a result of the function. Yet the function expects a function as the first argument. How can I deal with this problem? Thanks.

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• Using an element against an entire list in Haskell

  - by Snick

  I have an assignment and am currently caught in one section of what I'm trying to do. Without going in to specific detail here is the basic layout: I'm given a data element, f, that holds four different types inside (each with their own purpose): data F = F Float Int, Int a function: func :: F -> F-> Q Which takes two data elements and (by simple calculations) returns a type that is now an updated version of one of the types in the first f. I now have an entire list of these elements and need to run the given function using one data element and return the type's value (not the data element). My first analysis was to use a foldl function: myfunc :: F -> [F] -> Q myfunc y [] = func y y -- func deals with the same data element calls myfunc y (x:xs) = foldl func y (x:xs) however I keep getting the same error: "Couldn't match expected type 'F' against inferred type 'Q'. In the first argument of 'foldl', namely 'myfunc' In the expression: foldl func y (x:xs) I apologise for such an abstract analysis on my problem but could anyone give me an idea as to what I should do? Should I even use a fold function or is there recursion I'm not thinking about?

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• Are .NET's regular expressions Turing complete?

  - by Robert

  Regular expressions are often pointed to as the classical example of a language that is not Turning complete. For example "regular expressions" is given in as the answer to this SO question looking for languages that are not Turing complete. In my, perhaps somewhat basic, understanding of the notion of Turning completeness, this means that regular expressions cannot be used check for patterns that are "balanced". Balanced meaning have an equal number of opening characters as closing characters. This is because to do this would require you to have some kind of state, to allow you to match the opening and closing characters. However the .NET implementation of regular expressions introduces the notion of a balanced group. This construct is designed to let you backtrack and see if a previous group was matched. This means that a .NET regular expressions: ^(?<p>a)*(?<-p>b)*(?(p)(?!))$ Could match a pattern that: ab aabb aaabbb aaaabbbb ... etc. ... Does this means .NET's regular expressions are Turing complete? Or are there other things that are missing that would be required for the language to be Turing complete?

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• MySQL query puzzle - finding what WOULD have been the most recent date

  - by Hank

  I've looked all over and haven't yet found an intelligent way to handle this, though I feel sure one is possible: One table of historical data has quarterly information: CREATE TABLE Quarterly ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, PRIMARY KEY (unique_ID)); Another table of historical data (which is very large) contains daily information: CREATE TABLE Daily ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, qtr_ID INT UNSIGNED, PRIMARY KEY (unique_ID)); The qtr_ID field is not part of the feed of daily data that populated the database - instead, I need to retroactively populate the qtr_ID field in the Daily table with the Quarterly.unique_ID row ID, using what would have been the most recent quarterly data on that Daily.date_posted for that data source. For example, if the quarterly data is 101 2009-03-31 1 4.5 102 2009-06-30 1 4.4 103 2009-03-31 2 7.6 104 2009-06-30 2 7.7 105 2009-09-30 1 4.7 and the daily data is 1001 2009-07-14 1 3.5 ?? 1002 2009-07-15 1 3.4 && 1003 2009-07-14 2 2.3 ^^ then we would want the ?? qtr_ID field to be assigned '102' as the most recent quarter for that data source on that date, and && would also be '102', and ^^ would be '104'. The challenges include that both tables (particularly the daily table) are actually very large, they can't be normalized to get rid of the repetitive dates or otherwise optimized, and for certain daily entries there is no preceding quarterly entry. I have tried a variety of joins, using datediff (where the challenge is finding the minimum value of datediff greater than zero), and other attempts but nothing is working for me - usually my syntax is breaking somewhere. Any ideas welcome - I'll execute any basic ideas or concepts and report back.

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• JQuery autocomplete problem

  - by heffaklump

  Im using JQuerys Autocomplete plugin, but it doesn't autocomplete upon entering anything. Any ideas why it doesnt work? The basic example works, but not mine. var ppl = {"ppl":[{"name":"peterpeter", "work":"student"}, {"name":"piotr","work":"student"}]}; var options = { matchContains: true, // So we can search inside string too minChars: 2, // this sets autocomplete to begin from X characters dataType: 'json', parse: function(data) { var parsed = []; data = data.ppl; for (var i = 0; i < data.length; i++) { parsed[parsed.length] = { data: data[i], // the entire JSON entry value: data[i].name, // the default display value result: data[i].name // to populate the input element }; } return parsed; }, // To format the data returned by the autocompleter for display formatItem: function(item) { return item.name; } }; $('#inputplace').autocomplete(ppl, options); Ok. Updated: <input type="text" id="inputplace" /> So, when entering for example "peter" in the input field. No autocomplete suggestions appear. It should give "peterpeter" but nothing happens. And one more thing. Using this example works perfectly. var data = "Core Selectors Attributes Traversing Manipulation CSS Events Effects Ajax Utilities".split(" "); $("#inputplace").autocomplete(data);

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