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• What is the algorithm used by the memberwise equality test in .NET structs?

  - by Damian Powell

  What is the algorithm used by the memberwise equality test in .NET structs? I would like to know this so that I can use it as the basis for my own algorithm. I am trying to write a recursive memberwise equality test for arbitrary objects (in C#) for testing the logical equality of DTOs. This is considerably easier if the DTOs are structs (since ValueType.Equals does mostly the right thing) but that is not always appropriate. I would also like to override comparison of any IEnumerable objects (but not strings!) so that their contents are compared rather than their properties. This has proven to be harder than I would expect. Any hints will be greatly appreciated. I'll accept the answer that proves most useful or supplies a link to the most useful information. Thanks.

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• accessing values in a Map container, then try to match them

  - by wilson88

  Trying to compare the prices of the bids in the two maps.Sellers map and the buyers map. Conditions for comparison. 1) One bid is A and the other is B 2) Price of B i greater than price of A. I then copy the matched bids to a container called matched.I am not sure how to do the match of maps. map<int, Bid*> bidtable/Before matching map<int, Bid*> matched map<int, Bid*> unmatched

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• What are the major differences between Windows CE and Windows Mobile for a programmer?

  - by Brad Bruce

  What are the major differences between Windows CE and Windows Mobile for a programmer? I'd love to find a feature table, but haven't been able to find one on the Microsoft web site. I'm starting to work on a project involving industrial handheld terminals. I'm early into the design phase and need to find a comparison of Windows CE and Windows Mobile. Many of the people I'll be talking to jump on the first option that sounds "good enough". I want my first suggestion to be the best based on their needs. We're talking heavy duty hardware with a heavy duty price. I've got to get the programming questions out of the way early. We're currently a MFC6 and .Net 2.0 shop

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• Aggregate functions in ANSI SQL

  - by morpheous

  I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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• Java vs c++ types

  - by folone

  I've recently had a question about coledatetime java implementation, and Chris said, that the problem might lay in type conversions: cpp-float vs java-float (Or maybe cpp-date vs java-date. Not types, but..). Now I have several questions on this: Is there a table of comparison for java vs c++ types? If type conversions is the problem, in my situation (I have a db with OLEDate records, already created with some c++ program. I need to read and write to that db, so that the OLEDate field compatibility remained: my java code reads proper dates, and c++ program is not affected with what the java program wrote to the db.), what would you do: Use COleDateTime to retrieve the date with JNI? Create your own implementation at all costs (using broader types, or anything else)? Is there anything, I'm missing here?

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• I want to keep the values on textbox after onchange function

  - by user1908045

  hello i have problem with this code..I want to keep the values of the textboxes when the pageload and didnt write again the values. I have two drop down list. the First one is the country when the country selected then the page load and appear the city to select but afte the pageload the values on textbox is empty. I want to keep the values of textbox when the page load. This is the code <head> <script type="text/javascript"> function Load_id() { var Count = document.getElementById("Count").value; var Count_txt = "?Count=" location = Count_txt + Count } </script> <meta charset="UTF-8"> </head> <body> <div class="main"> <div class="headers"> <table> <tr><td rowspan="2"><img alt="unipi" src="/Images/logo.jpeg" height="75" width="52"></td> <td>University</td></tr> <tr><td>Data</td></tr> </table> </div> <div class="form"> <h3>Personal</h3><br/><br/><br/> <form id="Page1" name="Page1" action="Form1Sub.php" method="Post"> <table style="width:520px;text-align:left;"> <tr><td><label>Number:</label></td> <td><input type="text" required="required" id="AM" name="AM" value=""/></td> </tr> <tr><td><label>Name:</label></td> <td><input type="text" required="required" name="Name"/></td> </tr> <?php $host="localhost"; $username=""; $password=""; $dbName="Database"; $connection = mysql_connect($host, $username, $password) or die("Couldn't Connect to the Server"); $db = mysql_select_db($dbName, $connection) or die("cannot select DataBase"); $Count = $_GET['Count']; echo "<tr><td><label>Country</label></td>\n"; $country = mysql_query("select DISTINCT Country FROM lut_country_city "); echo " <td><select id=\"Count\" name=\"cat\" onChange=\"Load_id(this)\">\n"; echo " `<option>Select Country</option>\n"; while($nt=mysql_fetch_array($country)){ $selected = ($nt["Country"] == $Count)? "SELECTED":""; echo"<option value=\"".$nt['Country']."\"". $selected." >".$nt['Country']."</option>"; } echo " </select></td></tr>\n"; echo"<tr><td><label>City:</label></td>\n"; $q2 = mysql_query("Select id,City,Country FROM lut_country_city WHERE Country = '$Count'"); echo"<td><select name=\"SelectCity\">\n"; while($row = mysql_fetch_array($q2)) { echo"<option value=\"".$row['id']."\">".$row['City']."</option>"; } echo " </select></td></tr>\n"; ?> </table> <p> <button type="submit" id="Next">Next</button> </form> <form id="form1" action="index.php"> <button id="Back" type="submit">Back</button> </form> </p> </div> </div> </body> </html>

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• Learning about version control systems, Git, SVN

  - by anijhaw

  I am a basic SVN user now trying to learn GIT for a new position. I am trying the usual reading docs and watching videos. However after doing all that I still feel that there is a lot that I do not know. I was wondering if there is a place like project Euler for programming languages, that provides a series of exercises that you can do just to increase your confidence and test your knowledge about a version control system. Something thats generic enough and gets you up to speed with how to do basic things. This could also serve as a comparison point of sorts between multiple VCSs, that would show what things are easy in which VCS. If there is nothing I was planning to document my journey in learning GIT and the create an exercise of this sort.

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• Which is the best API/Library to use when accessing a WebCam in .Net?

  - by Doctor Jones

  Which is the best API to use when accessing a WebCam in .Net? (I know they can be webcam specific, I am willing to buy a new webcam if it means better results). I want to write a desktop application that will take video from a webcam and store it in MPEG4 formats (DivX, Xvid, etc...). I would also like to access bitmap stills from the device so I can do image comparison between frames. I have tried various libraries, and none have really been a great fit (some have performance issues (very inconsistent framerates), some have image quality limitations, some just crash out for seemingly no reason. I want to get high quality video (as high as I can get) and a decent framerate. My webcam is more than up to the job and I was hoping that there would be a nice Managed .Net library around that would help my cause. Are webcam APIs all just incredibly bad?

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• Why do date manipulation in Java with milliseconds?

  - by staticsan

  I was recently faced with the problem of calculating the number of days from two dates in Java (without using joda, I'm afraid). Searching on the 'net shows most answers to this question say to get the milliseconds of the two days and convert that to days, which I found appalling. However, a scant few show a different approach: use a temporary variable to count how many times it takes adding 1 day to the first date to get to the second. This leaves the conversions to the code that does it best: the library. Why do so many people advocate the first? In another project, I had previously encountered numerous subtle date calculation problems involving time-zones, daylight-saving and once even leap years using seconds to do date comparisions and calculations. All these went away when all the comparison and calculation code was rewitten to use the language libraries. (This was in PHP, though, where the libraries are structured quite differently to Java.) So I'm understandably reluctant to use this "common wisdom" in the world of Java about comparing dates.

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• How to convert an Info.plist file from mac os project to iphone project?

  - by Tom Pace

  I am developing an app for the iPhone OS devices, and am using a third-party engine which is not well documented but I've made great progress with it anyway. The problem: The engine's developer strongly urges extending from the existing template projects bundled with the engine, but the engine's Info.plist files are Mac OSX project Info.plist files. This is an iPhone engine, and so I cannot understand why the Info.plist file is structured to take keys for Mac OS apps, but that's how it is. I did a FileMerge comparison to ensure there was nothing within the file itself that defined its use for one OS or the other, so I guess it's defined somewhere in the project settings. Edit - Opening the plist file in Xcode or Property List Editor and then trying to add a key such as "Icon already includes gloss and bevel effects" will not work in this iPhone project because it is not in the list. However, "Cocoa Java Application" and others are available!

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• Insert multiple rows into temp table with one command in SQL2005

  - by Adam Haile

  I've got some data in the following format: -1,-1,-1,-1,701,-1,-1,-1,-1,-1,304,390,403,435,438,439,442,455 I need to insert it into a temp table like this: CREATE TABLE #TEMP ( Node int ) So that I can use it in a comparison with data in another table. The data above represents separate rows of the "Node" column. Is there an easy way to insert this data, all in one command? Also, the data will actually being coming in as seen, as a string... so I need to be able to just concat it into the SQL query string. I can obviously modify it first if needed.

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• C++: Comparing list of doubles with some invalid values (QNAN)

  - by J.M.

  Hello, i need to compare two std::list < double , but some doubles may be invalid numbers (QNAN). If any invalid numbers are list entries the compare process won't work, because a comparison of the same invalid value will always result in 'false'. What is the easiest and most elegant way to solve the problem? My idea was to create copies of both lists, iterate through them and remove invalid values and then compare the remaining lists. The lists will typically have 20-50 values in them. Is there a more resource friendly way to solve it?

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• MD5 hash validation failing for unknown reason in PHP

  - by Sennheiser

  I'm writing a login form, and it converts the given password to an MD5 hash with md5($password), then matches it to an already-hashed record in my database. I know for sure that the database record is correct in this case. However, it doesn't log me in and claims the password is incorrect. Here's my code: $password = mysql_real_escape_string($_POST["password"]); ...more code... $passwordQuery = mysql_fetch_row(mysql_query(("SELECT password FROM users WHERE email = '$userEmail'"))); ...some code... elseif(md5($password) != $passwordQuery) { $_SESSION["noPass"] = "That password is incorrect."; } ...more code after... I tried pulling just the value of md5($password) and that matched up when I visually compared it. However, I can't get the comparison to work in PHP. Perhaps it is because the MySQL record is stored as text, and the MD5 is something else?

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• Java 7 API design best practice - return Array or return Collection

  - by Shengjie

  I know this question has be asked before generic comes out. Array does win out a bit given Array enforces the return type, it's more type-safe. But now, with latest JDK 7, every time when I design this type of APIs: public String[] getElements(String type) vs public List<String> getElements(String type) I am always struggling to think of some good reasons to return A Collection over An Array or another way around. What's the best practice when it comes to the case of choosing String[] or List as the API's return type? Or it's courses for horses. I don't have a special case in my mind, I am more looking for a generic pros/cons comparison.

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• Append to a file in Java. Is it a joke?

  - by Roman

  I need to append some data to existing file. I started to browse Internet to find out how to do it. And I found this mini (as they say) application to do that: http://www.devdaily.com/java/edu/qanda/pjqa00009.shtml Well I was already annoyed by the fact how complicated are things in Java (in comparison with Python, for example). But this is too much! I just want to add to a file! It should be one line! Not 50! Or do I get something wrong?

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• How do I choose a database?

  - by liamzebedee

  I need a comparison table of some sort for database varieties (MySQL, SQLite etc.). I can't find one. My use case is, I am implementing storage of objects in a distributed hash table. I need a database solution that is: Fast for sorting Simplistic (no users, preferably no additional structures like multiple tables etc.) Concurrent (if possible) Multi-platform File based (not stored in memory primarily) Centralized I will be programming in Go. As I understand, I believe I need what is called a Document Orientated Database, because I am storing objects, identified by keys. EDIT: While I am implementing a DHT, I will also be storing metadata about the objects, such as access counts etc. It would also be preferable to have TLL (time to live)

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• Drive space hungry NoSQL's databases

  - by forum_inquisitor

  I've tested NoSQL databases like CouchDB, MongoDB and Cassandra and observed tendence to absorbing very large amount of drive space relative to inserted key-value pairs. When comparing CouchDB and MySQL schemaless databases CouchDB is consuming much more drive space than MySQL. I know about that key-value DBs by default are versioning and have long uuid and need key optimalisation - the comparison was between about 15 mln rows in MySQL and 1-5 mln documents listed NoSQL DB's. My question is : Is there any NoSQL with good compaction / compression of data? So that I can have NoSQL database with a size closer to 5GB than 50GB?

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• comparing two end() iterators

  - by aafoo

  list<int> foo; list<int> foo2; list<int>::iterator foo_end = foo.end(); list<int>::iterator foo2_end = foo2.end(); for (list<int>::iterator it = foo.begin(); it != foo2_end; ++foo) <- notice != comparison here { ... it this allowed? will it work correctly. I am inclined to think that this is implementation dependent, anyone knows if standard says anything about this?

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• Filtering forms in MS Access

  - by terence6

  I have a simple form showing products from my database. Each product has a foreign key to manufacturer_id . I would like to filter my form by manufacturer_id instead of default product_id. How I can do that ? I know I must create a macro. Also I've already created a query, that takes manufacturer's name as argument and returns manufacturer_id. So basically it should work in this way, that when I press 'Filter' button on my form, it runs macro that opens my query asking for manufacturer's name. And when the name is returned the whole form is filtered (so somewhere there should be comparison between manufacturer_id in product and that returned from query, but I can't manage to do that). I'm using access 2007. Model:

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• Deciphering Encoding: Packet Analyzation Tools

  - by Zombies

  I am looking for better tools than wireshark for this. The problem with wireshark is that it does not format the data layer (which is the only part I am looking at) cleanly for me to compare the different packets and attempt to understand the third party encoding (which is closed source). Specifically, what are some good tools for viewing data, and not tcp/udp header information? Particularly, a tool that formats the data for comparison. To be very specific: I would like a program that compares multiple (not just 2) files in hex.

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• weird space in IE - Any suggestions?

  - by Guru

  The below table is the only element inside a body tag - This displays fine in Firefox 3 as i expect it to be but it does not look good in IE7. There is a weird space just between the nested table and the row above. Can you please suggest some way to remove that weird space? - Thanks <table> <tr> <td colspan="14"> <div> <table id="value_table" width="100%" border="0" cellspacing="0" cellpadding="2" style="border-collapse: collapse; display: block"> <tr> <td height="20" align="center" valign="Middle" class="Header"> <div align="left"><b>  Search Relationships</b></div> </td> </tr> <tr> <td>This is working</td> </tr> <tr valign="top"> <td>second row</td> <td nowrap="nowrap" class="GrayRow" valign="top" border="1" height="40" align="center" style="border: none"> just above the table <table border="1" cellpadding="0" cellspacing="0" align="left"> <tr valign="top"> <td>new row inside table</td> <td class="GrayRow" nowrap="nowrap"> <b>Select:</b>   <select id="j_id19:browseType" name="j_id19:browseType" size="1" class="TextBlackNormal" onchange="showDynamicBox(this);"> <option value="NAME">User Name</option> <option value="ID">User Id</option> <option value="IBD/Office/IP">IBD/Office /IP</option> <option value="APA#">APA#</option></select>    </td> <td> <div id="dynamicBox1" style="display: block"><input id="j_id19:j_id23" name="j_id19:j_id23" type="text" value="" size="32" class="TextBlackNormal" /></div> </td>     <td> <div id="dynamicBox2" style="display: none"><input id="j_id19:j_id25" name="j_id19:j_id25" type="text" value="" size="32" class="TextBlackNormal" /></div> </td>     <td> <div id="dynamicBox3" style="display: none"> IBD   <input id="j_id19:ibdval1" name="j_id19:ibdval1" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" />   OFF   <input id="j_id19:ibdval2" name="j_id19:ibdval2" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" />   IP    <input id="j_id19:ibdval3" name="j_id19:ibdval3" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" /> </div> </td>     <td> <div id="dynamicBox4" style="display: none"> Average Price Account#    <input id="j_id19:apaval1" name="j_id19:apaval1" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" />  <input id="j_id19:apaval2" name="j_id19:apaval2" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" />  <input id="j_id19:apaval3" name="j_id19:apaval3" type="text" value="" maxlength="3" size="3" onkeyup="goToNextFocus(this);" class="TextBlackNormal" /> </div> </td>        <td class="GrayRow" nowrap="nowrap"> <div id="msg_multiple_inputs" style="display:none"> <font color="#990000" size="1">Enter multiple separated by commas   </font> </div>                                   </td> <td><input id="j_id19:display" name="j_id19:display" type="submit" value="Display" class="TextBlackNormal" /></td> </tr> </table> </td> </tr> </table> </div> </td> </tr> </table>

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• Why do people develop emotional attachments for programming languages?

  - by Andrew Heath

  Aside from people who actually developed the languages, I really don't get how someone can develop passion/attachment/perhaps even obsession for a programming language... yet not a day goes by that I don't see a programmer exhibiting this behavior on the internet. I understand how people can feel this way regarding spoken languages - but there's a whole boatload of culture, history, etc that come attached with them. By comparison, the "Python Culture" (as an example) is so small as to be wholly insignificant. Does everyone have a language they love? Am I the odd one out? The dirty polygamist? Are these people rational or silly?

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• How do I make this Query against EF Efficient?

  - by dudeNumber4

  Using EF4. Assume I have this: IQueryable<ParentEntity> qry = myRepository.GetParentEntities(); Int32 n = 1; What I want to do is this, but EF can't compare against null. qry.Where( parent => parent.Children.Where( child => child.IntCol == n ) != null ) What works is this, but the SQL it produces (as you would imagine) is pretty inefficient: qry.Where( parent => parent.Children.Where( child => child.IntCol == n ).FirstOrDefault().IntCol == n ) How can I do something like the first comparison to null that won't be generating nested queries and so forth?

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• C++ - how does Sleep() and cin work?

  - by quano

  Just curious. How does actually the function Sleep() work (declared in windows.h)? Maybe not just that implementation, but anyone. With that I mean - how is it implemented? How can it make the code "stop" for a specific time? Also curious about how cin and those actually work. What do they do exactly? The only way I know how to "block" something from continuing to run is with a while loop, but considering that that takes a huge amount of processing power in comparison to what's happening when you're invoking methods to read from stdin (just compare a while (true) to a read from stdin), I'm guessing that isn't what they do.

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• typeof === "undefined" vs. != null

  - by Thor Thurn

  I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. It's needed because 'undefined' could be renamed, though. My question is: How is that code any better than this approach: if (input != null) { // do stuff } As far as I know, you can't redefine null, so it's not going to break unexpectedly. And, because of the type-coercion of the != operator, this checks for both undefined and null... which is often exactly what you want (e.g. for optional function parameters). Yet this form does not seem widespread, and it even causes JSLint to yell at you for using the evil != operator. Why is this considered bad style?

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