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  • A C# Refactoring Question...

    - by james lewis
    I came accross the following code today and I didn't like it. It's fairly obvious what it's doing but I'll add a little explanation here anyway: Basically it reads all the settings for an app from the DB and the iterates through all of them looking for the DB Version and the APP Version then sets some variables to the values in the DB (to be used later). I looked at it and thought it was a bit ugly - I don't like switch statements and I hate things that carry on iterating through a list once they're finished. So I decided to refactor it. My question to all of you is how would you refactor it? Or do you think it even needs refactoring at all? Here's the code: using (var sqlConnection = new SqlConnection(Lfepa.Itrs.Framework.Configuration.ConnectionString)) { sqlConnection.Open(); var dataTable = new DataTable("Settings"); var selectCommand = new SqlCommand(Lfepa.Itrs.Data.Database.Commands.dbo.SettingsSelAll, sqlConnection); var reader = selectCommand.ExecuteReader(); while (reader.Read()) { switch (reader[SettingKeyColumnName].ToString().ToUpper()) { case DatabaseVersionKey: DatabaseVersion = new Version(reader[SettingValueColumneName].ToString()); break; case ApplicationVersionKey: ApplicationVersion = new Version(reader[SettingValueColumneName].ToString()); break; default: break; } } if (DatabaseVersion == null) throw new ApplicationException("Colud not load Database Version Setting from the database."); if (ApplicationVersion == null) throw new ApplicationException("Colud not load Application Version Setting from the database."); }

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  • Unresolved external symbol error in c++

    - by Crystal
    I am trying to do a simple hw problem involving namespace, static data members and functions. I am getting an unresolved external symbol error Error 1 error LNK2001: unresolved external symbol "private: static double JWong::SavingsAccount::annualInterestRate" (?annualInterestRate@SavingsAccount@JWong@@0NA) SavingsAccount.obj SavingsAccount And I don't see why I am getting this error. Maybe I don't know something about static variables compared to regular data members that is causing this error. Here is my code: SavingsAccount.h file #ifndef JWONG_SAVINGSACCOUNT_H #define JWONG_SAVINGSACCOUNT_H namespace JWong { class SavingsAccount { public: // default constructor SavingsAccount(); // constructor SavingsAccount(double savingsBalance); double getSavingsBalance(); void setSavingsBalance(double savingsBalance); double calculateMonthlyInterest(); // static functions static void modifyInterestRate(double newInterestRate); static double getAnnualInterestRest(); private: double savingsBalance; // static members static double annualInterestRate; }; } #endif SavingsAccount.cpp file #include <iostream> #include "SavingsAccount.h" // default constructor, set savingsBalance to 0 JWong::SavingsAccount::SavingsAccount() : savingsBalance(0) {} // constructor JWong::SavingsAccount::SavingsAccount(double savingsBalance) : savingsBalance(savingsBalance) {} double JWong::SavingsAccount::getSavingsBalance() { return savingsBalance; } void JWong::SavingsAccount::setSavingsBalance(double savingsBalance) { this->savingsBalance = savingsBalance; } // returns monthly interest and sets savingsBalance to new amount double JWong::SavingsAccount::calculateMonthlyInterest() { double monthlyInterest = savingsBalance * SavingsAccount::annualInterestRate / 12; setSavingsBalance(savingsBalance + monthlyInterest); return monthlyInterest; } void JWong::SavingsAccount::modifyInterestRate(double newInterestRate) { SavingsAccount::annualInterestRate = newInterestRate; } double JWong::SavingsAccount::getAnnualInterestRest() { return SavingsAccount::annualInterestRate; }

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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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  • URL development and mod_rewrite

    - by iRector
    My site is made-up of the main page, and multiple sub-directories, all under the same domain. My URLS are currently like .................| Ideal clean version: mysite.com mysite.com/?content=content1 ......................| mysite.com/content1/ mysite.com/?content=content2&page=4 ........| mysite.com/content2/4/ mysite.com/?content=content3 ......................| mysite.com/content3/ mysite.com/?content=content4 ......................| mysite.com/content4/ mysite.com/?content=article&id=34 ............| mysite.com/article/34/ Then the sub-directories are essentially the same: mysite.com/subdir, mysite.com/subdir2, mysite.com/subdir3, etc mysite.com/subdir/?content=content1 ...................| mysite.com/subdir/content1/ mysite.com/subdir/?content=content2&page=4 .....| mysite.com/subdir/content2/4/ mysite.com/subdir/?content=content3 ...................| mysite.com/subdir/content3/ mysite.com/subdir/?content=content4 ...................| mysite.com/subdir/content4/ mysite.com/subdir/?content=article&id=34 .........| mysite.com/subdir/article/34/ I've used mod_rewrite briefly, but I'm not sure how to approach these multiple variables. Also, how would I differentiate between the actually subfolders, and the content variable. As so to prevent 'subdir' or 'subdir2' from being plugged in as the content variable for the root site. I've played around with plenty of code snippets, but I've wiped my .htaccess slate clean, and approach you all in an attempt to help me repopulate it. Your input would thoroughly be appreciated. Note: The only time the page query string will be needed is when 'content' == 'content2' ?content=content2&page=4 **Same rule is shared by the article/id relationship, all other 'content' values are expected to be dynamic.

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  • How do I build a filtered_streambuf based on basic_streambuf?

    - by swestrup
    I have a project that requires me to insert a filter into a stream so that outgoing data will be modified according to the filter. After some research, it seems that what I want to do is create a filtered_streambuf like this: template <class StreamBuf class filtered_streambuf: public StreamBuf { ... } And then insert a filtered_streambuf<> into whichever stream I need to be filtered. My problem is that I don't know what invariants I need to maintain while filtering a stream, in order to ensure that Derived classes can work as expected. In particular, I may find I have filtered_streambufs built over other filtered_streambufs. All the various stream inserters, extractors and manipulators work as expected. The trouble is that I just can't seem to work out what the minimal interface is that I need to supply in order to guarantee that an iostream will have what it needs to work correctly. In particular, do I need to fake the movement of the protected pointer variables, or not? Do I need a fake data buffer, or not? Can I just override the public functions, rewriting them in terms of the base streambuf, or is that too simplistic?

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  • Regex: match a non nested code block

    - by Sylvanas Garde
    I am currently writing a small texteditor. With this texteditor users are able to create small scripts for a very simple scripting engine. For a better overview I want to highlight codeblocks with the same command like GoTo(x,y) or Draw(x,y). To achieve this I want to use Regular Expresions (I am already using it to highlight other things like variables) Here is my Expression (I know it's very ugly): /(?<!GoTo|Draw|Example)(^(?:GoTo|Draw|Example)\(.+\)*?$)+(?!GoTo|Draw|Example)/gm It matches the following: lala GoTo(5656) -> MATCH 1 sdsd GoTo(sdsd) --comment -> MATCH 2 GoTo(23329); -> MATCH 3 Test() GoTo(12) -> MATCH 4 LALA Draw(23) -> MATCH 5 Draw(24) -> MATCH 6 Draw(25) -> MATCH 7 But what I want to achieve is, that the complete "blocks" of the same command are matched. In this case Match 2 & 4 and Match 5 & 6 & 7 should be one match. Tested with http://regex101.com/, the programming lanuage is vb.net. Any advise would be very useful, Thanks in advance!

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  • Why NOT use POST method here?

    - by Camran
    I have a classifieds website. In the main page (index) I have several form fields which the user may or may not fill in, in order to specify a detailed search of classifieds. Ex: Category: Cars Price from: 3000 Price to: 10000 Color: Red Area: California The forms' action is set to a php page: <form action='query_sql.php' method='post'> In query_sql.php I fetch the variables like this: category=$_POST['category']; etc etc... Then query MySql: $query="SELECT........WHERE category='$category' etc etc.... $results = mysql_query($query); Then I simply display the results of the query to the user by creating a table which is filled in dynamically depending on the results set. However, according to an answer by Col. Shrapnel in my previous Q I shouldn't use POST here: http://stackoverflow.com/questions/3004754/how-to-hide-url-from-users-when-submitting-this-form The reason I use post is simply to hide the "one-page-word-document" long URL in the browsers adress bar. I am very confused, is it okay to use POST or not? It is working fine both when I use GET or POST now... And it is already on a production server... Btw, in the linked question, I wasn't referring to make URL invisible (or hide it) I just wanted it too look better (which I have accomplished with mod_rewrite). UPDATE: If I use GET, then how should I make the url better looking (beautiful)? Check this previous Q out: http://stackoverflow.com/questions/3000524/how-to-make-this-very-long-url-appear-short

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  • Filtering a PHP array containing dates into a yearly summary

    - by privateace
    I'm looking at a way to create a summary of transactions within a certain month based on the contents of a PHP array. Intended outcome (excusing layout): ------------------------------------------- | December 2009 | 12 | | January 2010 | 02 | | February 2010 | 47 | | March 2010 | 108 | | April 2010 | 499 | ------------------------------------------- Based on my array: Array ( [0] => Array ( [name] => 2009-10-23 [values] => Array ( [0] => INzY2MTI4ZWM4OGRm ) ) [1] => Array ( [name] => 2009-10-26 [values] => Array ( [0] => IYmIzOWNmMmU3OWQz ) ) [2] => Array ( [name] => 2009-11-23 [values] => Array ( [0] => INTg4YzgxYWU1ODkx [1] => IMjhkNDZkY2FjNDhl ) ) [3] => Array ( [name] => 2009-11-24 [values] => Array ( [0] => INTg4YzgxYWU1ODkx [1] => INTg4YzgxYWU1ODkx ) ) [4] => Array ( [name] => 2009-12-01 [values] => Array ( [0] => IMWFiODk5ZjU1OTFk ) ) I've had absolutely no luck no matter what I've tried. Especially with adding months that do not contain any variables.

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  • facebook authentication / login trouble

    - by salmane
    I have setup facebook authentication using php and it goes something like this first getting the authorization here : https://graph.facebook.com/oauth/authorize?client_id=<?= $facebook_app_id ?>&redirect_uri=http://www.example.com/facebook/oauth/&scope=user_about_me,publish_stream then getting the access Token here : $url = "https://graph.facebook.com/oauth/access_token?client_id=".$facebook_app_id."&redirect_uri=http://www.example.com/facebook/oauth/&client_secret=".$facebook_secret."&code=".$code;" function get_string_between($string, $start, $end){ $string = " ".$string; $ini = strpos($string,$start); if ($ini == 0) return ""; $ini += strlen($start); $len = strpos($string,$end,$ini) - $ini; return substr($string,$ini,$len); } $access_token = get_string_between(file_get_contents($url), "access_token=", "&expires="); then getting user info : $facebook_user = file_get_contents('https://graph.facebook.com/me?access_token='.$access_token); $facebook_id = json_decode($facebook_user)->id; $first_name = json_decode($facebook_user)->first_name; $last_name = json_decode($facebook_user)->last_name; this is pretty ugly ( in my opinion ) but it works....how ever....the user is still not logged in...because i did not create or retrieve any session variables to confirm that the user is logged in to facebook... which means that after getting the authentication done the use still has to login .... first: is there a better way using php to do what i did above ? second: how do i set/ get session variable / cookies that ensure that the user doesnt have to click login thanks for your help

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  • Finding cause of memory leaks in large PHP stacks

    - by Mike B
    I have CLI script that runs over several thousand iterations between runs and it appears to have a memory leak. I'm using a tweaked version of Zend Framework with Smarty for view templating and each iteration uses several MB worth of code. The first run immediately uses nearly 8MB of memory (which is fine) but every following run adds about 80kb. My main loop looks like this (very simplified) $users = UsersModel::getUsers(); foreach($users as $user) { $obj = new doSomethingAwesome(); $obj->run($user); $obj = null; unset($obj); } The point is that everything in scope should be unset and the memory freed. My understanding is that PHP runs through its garbage collection process at it's own desire but it does so at the end of functions/methods/scripts. So something must be leaking memory inside doSomethingAwesome() but as I said it is a huge stack of code. Ideally, I would love to find some sort of tool that displayed all my variables no matter the scope at some point during execution. Some sort of symbol-table viewer for php. Does anything like that or any other tools that could help nail down memory leaks in php exist?

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  • PHP Preserve scope when calling a function

    - by Joshua
    I have a function that includes a file based on the string that gets passed to it i.e. the action variable from the query string. I use this for filtering purposes etc so people can't include files they shouldn't be able to and if the file doesn't exist a default file is loaded instead. The problem is that when the function runs and includes the file scope, is lost because the include ran inside a function. This becomes a problem because I use a global configuration file, then I use specific configuration files for each module on the site. The way I'm doing it at the moment is defining the variables I want to be able to use as global and then adding them into the top of the filtering function. Is there any easier way to do this, i.e. by preserving scope when a function call is made or is there such a thing as PHP macros? Edit: Would it be better to use extract($_GLOBALS); inside my function call instead? Edit 2: For anyone that cared. I realised I was over thinking the problem altogether and that instead of using a function I should just use an include, duh! That way I can keep my scope and have my cake too.

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  • Trouble with pointers and references in C++

    - by KingNestor
    I have a PolygonList and a Polygon type, which are std::lists of Points or lists of lists of points. class Point { public: int x, y; Point(int x1, int y1) { x = x1; y = y1; } }; typedef std::list<Point> Polygon; typedef std::list<Polygon> PolygonList; // List of all our polygons PolygonList polygonList; However, I'm confused on reference variables and pointers. For example, I would like to be able to reference the first Polygon in my polygonList, and push a new Point to it. So I attempted to set the front of the polygonList to a Polygon called currentPolygon like so: Polygon currentPolygon = polygonList.front(); currentPolygon.push_front(somePoint); and now, I can add points to currentPolygon, but these changes end up not being reflected in that same polygon in the polygonList. Is currentPolygon simply a copy of the Polygon in the front of polygonList? When I later iterate over polygonList all the points I've added to currentPolygon aren't shown. It works if I do this: polygonList.front().push_front(somePoint); Why aren't these the same and how can I create a reference to the physical front polygon rather than a copy of it?

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  • C++ converting back and forth from derived and base classes

    - by user127817
    I was wondering if there is a way in C++ to accomplish the following: I have a base class called ResultBase and two class that are Derived from it, Variable and Expression. I have a few methods that do work on vector<ResultBase> . I want to be able to pass in vectors of Variable and Expression into these methods. I can achieve this by creating a vector<ResultBase> and using static_cast to fill it with the members from my vector of Variable/Expression. However, once the vector has run through the methods, I want to be able to get it back as the vector of Result/Expression. I'll know for sure which one I want back. static_cast won't work here as there isn't a method to reconstruct a Variable/Expression from a ResultBase, and more importantly I wouldn't have the original properties of the Variables/Expressions The methods modify some of the properties of the ResultBase and I need those changes to be reflected in the original vectors. (i.e. ResultBase has a property called IsLive, and one of the methods will modify this property. I want this IsLive value to be reflected in the derived class used to create the ResultBase Whats the easiest way to accomplish this?

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  • SQL wont work? It doesn't come up with errors either

    - by Stefan
    Hey there, I have php function which checks to see if variables are set and then adds them onto my sql query. However I am don't seem to be getting any results back!? $where_array = array(); if (array_key_exists("location", $_GET)) { $location = addslashes($_GET['location']); $where_array[] = "`mainID` = '".$location."'"; } if (array_key_exists("gender", $_GET)) { $gender = addslashes($_GET["gender"]); $where_array[] = "`gender` = '".$gender."'"; } if (array_key_exists("hair", $_GET)) { $hair = addslashes($_GET["hair"]); $where_array[] = "`hair` = '".$hair."'"; } if (array_key_exists("area", $_GET)) { $area = addslashes($_GET["area"]); $where_array[] = "`locationID` = '".$area."'"; } $where_expr = ''; if ($where_array) { $where_expr = "WHERE " . implode(" AND ", $where_array); } $sql = "SELECT `postID` FROM `posts` ". $where_expr; $dbi = new db(); $result = $dbi->query($sql); $r = mysql_fetch_row($result); I'm trying to call the data after in a list like so: $dbi = new db(); $offset = ($currentpage - 1) * $rowsperpage; // get the info from the db $sql .= " ORDER BY `time` DESC LIMIT $offset, $rowsperpage"; $result = $dbi->query($sql); // while there are rows to be fetched... while ($row = mysql_fetch_object($result)){ // echo data echo $row['text']; } // end while Anyone got any ideas why I am not retrieving any data? -Stefan

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  • Initialising vals which might throw an exception

    - by Paul Butcher
    I need to initialise a set of vals, where the code to initialise them might throw an exception. I'd love to write: try { val x = ... generate x value ... val y = ... generate y value ... } catch { ... exception handling ... } ... use x and y ... But this (obviously) doesn't work because x and y aren't in scope outside of the try. It's easy to solve the problem by using mutable variables: var x: Whatever = _ var y: Whatever = _ try { x = ... generate x value ... y = ... generate y value ... } catch { ... exception handling ... } ... use x and y ... But that's not exactly very nice. It's also easy to solve the problem by duplicating the exception handling: val x = try { ... generate x value ... } catch { ... exception handling ... } val y = try { ... generate y value ... } catch { ... exception handling ... } ... use x and y ... But that involves duplicating the exception handling. There must be a "nice" way, but it's eluding me.

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  • How to store and remove dynamically and automatic variable of generic data type in custum list data

    - by Vineel Kumar Reddy
    Hi I have created a List data structure implementation for generic data type with each node declared as following. struct Node { void *data; .... .... } So each node in my list will have pointer to the actual data(generic could be anything) item that should be stored in the list. I have following signature for adding a node to the list AddNode(struct List *list, void* eledata); the problem is when i want to remove a node i want to free even the data block pointed by *data pointer inside the node structure that is going to be freed. at first freeing of datablock seems to be straight forward free(data) // forget about the syntax..... But if data is pointing to a block created by malloc then the above call is fine....and we can free that block using free function int *x = (int*) malloc(sizeof(int)); *x = 10; AddNode(list,(void*)x); // x can be freed as it was created using malloc what if a node is created as following int x = 10; AddNode(list,(void*)&x); // x cannot be freed as it was not created using malloc Here we cannot call free on variable x!!!! How do i know or implement the functionality for both dynamically allocated variables and static ones....that are passed to my list.... Thanks in advance...

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  • iOS - Passing variable to view controller

    - by gj15987
    I have a view with a view controller and when I show this view on screen, I want to be able to pass variables to it from the calling class, so that I can set the values of labels etc. First, I just tried creating a property for one of the labels, and calling that from the calling class. For example: SetTeamsViewController *vc = [[SetTeamsViewController alloc] init]; vc.myLabel.text = self.teamCount; [self presentModalViewController:vc animated:YES]; [vc release]; However, this didn't work. So I tried creating a convenience initializer. SetTeamsViewController *vc = [[SetTeamsViewController alloc] initWithTeamCount:self.teamCount]; And then in the SetTeamsViewController I had - (id)initWithTeamCount:(int)teamCount { self = [super initWithNibName:nil bundle:nil]; if (self) { // Custom initialization self.teamCountLabel.text = [NSString stringWithFormat:@"%d",teamCount]; } return self; } However, this didn't work either. It's just loading whatever value I've given the label in the nib file. I've littered the code with NSLog()s and it is passing the correct variable values around, it's just not setting the label. Any help would be greatly appreciated. EDIT: I've just tried setting an instance variable in my designated initializer, and then setting the label in viewDidLoad and that works! Is this the best way to do this? Also, when dismissing this modal view controller, I update the text of a button in the view of the calling ViewController too. However, if I press this button again (to show the modal view again) whilst the other view is animating on screen, the button temporarily has it's original value again (from the nib). Does anyone know why this is?

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  • C++ Constructor initialization list strangeness

    - by Andy
    I have always been a good boy when writing my classes, prefixing all member variables with m_: class Test { int m_int1; int m_int2; public: Test(int int1, int int2) : m_int1(int int1), m_int2(int int2) {} }; void main() { Test t(10, 20); // Just an example } However, recently I forgot to do that and ended up writing: class Test { int int1; int int2; public: // Very questionable, but of course I meant to assign ::int1 to this->int1! Test(int int1, int int2) : int1(int1), int2(int2) {} }; Believe it or not, the code compiled with no errors/warnings and the assignments took place correctly! It was only when doing the final check before checking in my code when I realised what I had done. My question is: why did my code compile? Is something like that allowed in the C++ standard, or is it simply a case of the compiler being clever? In case you were wondering, I was using Visual Studio 2008 Thank you.

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  • How Can I Find What's Causing My Transaction to Get Promoted?

    - by Damian Powell
    I have web site which serves web services (a mixture of .asmx and WCF) which is mostly using LINQ to SQL and System.Transactions. Occaisionally we see the transaction get promoted to a distributed transaction which causes problems because our web servers are isolated from our databases in such a way that it is not possible for us to use MSDTC. I have configured tracing for System.Transactions by adding the following to my web.config: <system.diagnostics> <sources> <source name="System.Transactions" switchValue="Information"> <listeners> <add name="tx" type="System.Diagnostics.XmlWriterTraceListener" initializeData="tx.log" /> </listeners> </source> </sources> </system.diagnostics> It's very interesting and shows me when the transaction is promoted, but I find that it doesn't really help be discover why. Is there an equivalent tracing mechanism for ADO.NET that will show me when connections are created, including the variables that affect pooling (user, cnn string, transaction scope)?

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  • How can I pass in a params of Expression<Func<T, object>> to a method?

    - by Pure.Krome
    Hi folks, I have the following two methods :- public static IQueryable<T> IncludeAssociations<T>(this IQueryable<T> source, params string[] associations) { ... } public static IQueryable<T> IncludeAssociations<T>(this IQueryable<T> source, params Expression<Func<T, object>>[] expressions) { ... } Now, when I try and pass in a params of Expression<Func<T, object>>[], it always calls the first method (the string[]' and of course, that value isNULL`) Eg. Expression<Func<Order, object>> x1 = x => x.User; Expression<Func<Order, object>> x2 = x => x.User.Passport; var foo = _orderRepo .Find() .IncludeAssociations(new {x1, x2} ) .ToList(); Can anyone see what I've done wrong? Why is it thinking my params are a string? Can I force the type, of the 2x variables?

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  • R: Are there any alternatives to loops for subsetting from an optimization standpoint?

    - by Adam
    A recurring analysis paradigm I encounter in my research is the need to subset based on all different group id values, performing statistical analysis on each group in turn, and putting the results in an output matrix for further processing/summarizing. How I typically do this in R is something like the following: data.mat <- read.csv("...") groupids <- unique(data.mat$ID) #Assume there are then 100 unique groups results <- matrix(rep("NA",300),ncol=3,nrow=100) for(i in 1:100) { tempmat <- subset(data.mat,ID==groupids[i]) #Run various stats on tempmat (correlations, regressions, etc), checking to #make sure this specific group doesn't have NAs in the variables I'm using #and assign results to x, y, and z, for example. results[i,1] <- x results[i,2] <- y results[i,3] <- z } This ends up working for me, but depending on the size of the data and the number of groups I'm working with, this can take up to three days. Besides branching out into parallel processing, is there any "trick" for making something like this run faster? For instance, converting the loops into something else (something like an apply with a function containing the stats I want to run inside the loop), or eliminating the need to actually assign the subset of data to a variable?

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  • How to handle 'this' pointer in constructor?

    - by Kyle
    I have objects which create other child objects within their constructors, passing 'this' so the child can save a pointer back to its parent. I use boost::shared_ptr extensively in my programming as a safer alternative to std::auto_ptr or raw pointers. So the child would have code such as shared_ptr<Parent>, and boost provides the shared_from_this() method which the parent can give to the child. My problem is that shared_from_this() cannot be used in a constructor, which isn't really a crime because 'this' should not be used in a constructor anyways unless you know what you're doing and don't mind the limitations. Google's C++ Style Guide states that constructors should merely set member variables to their initial values. Any complex initialization should go in an explicit Init() method. This solves the 'this-in-constructor' problem as well as a few others as well. What bothers me is that people using your code now must remember to call Init() every time they construct one of your objects. The only way I can think of to enforce this is by having an assertion that Init() has already been called at the top of every member function, but this is tedious to write and cumbersome to execute. Are there any idioms out there that solve this problem at any step along the way?

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  • Can C++ do something like an ML case expression?

    - by Nathan Andrew Mullenax
    So, I've run into this sort of thing a few times in C++ where I'd really like to write something like case (a,b,c,d) of (true, true, _, _ ) => expr | (false, true, _, false) => expr | ... But in C++, I invariably end up with something like this: bool c11 = color1.count(e.first)>0; bool c21 = color2.count(e.first)>0; bool c12 = color1.count(e.second)>0; bool c22 = color2.count(e.second)>0; // no vertex in this edge is colored // requeue if( !(c11||c21||c12||c22) ) { edges.push(e); } // endpoints already same color // failure condition else if( (c11&&c12)||(c21&&c22) ) { results.push_back("NOT BICOLORABLE."); return true; } // nothing to do: nodes are already // colored and different from one another else if( (c11&&c22)||(c21&&c12) ) { } // first is c1, second is not set else if( c11 && !(c12||c22) ) { color2.insert( e.second ); } // first is c2, second is not set else if( c21 && !(c12||c22) ) { color1.insert( e.second ); } // first is not set, second is c1 else if( !(c11||c21) && c12 ) { color2.insert( e.first ); } // first is not set, second is c2 else if( !(c11||c21) && c22 ) { color1.insert( e.first ); } else { std::cout << "Something went wrong.\n"; } I'm wondering if there's any way to clean all of those if's and else's up, as it seems especially error prone. It would be even better if it were possible to get the compiler complain like SML does when a case expression (or statement in C++) isn't exhaustive. I realize this question is a bit vague. Maybe, in sum, how would one represent an exhaustive truth table with an arbitrary number of variables in C++ succinctly? Thanks in advance.

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  • SSRS code variable resetting on new page

    - by edmicman
    In SSRS 2008 I am trying to maintain a SUM of SUMs on a group using custom Code. The reason is that I have a table of data, grouped and returning SUMs of the data. I have a filter on the group to remove lines where group sums are zero. Everything works except I'm running into problems with the group totals - it should be summing the visible group totals but is instead summing the entire dataset. There's tons of articles about how to work around this, usually using custom code. I've made custom functions and variables to maintain a counter: Public Dim GroupMedTotal as Integer Public Dim GrandMedTotal as Integer Public Function CalcMedTotal(ThisValue as Integer) as Integer GroupMedTotal = GroupMedTotal + ThisValue GrandMedTotal = GrandMedTotal + ThisValue Return ThisValue End Function Public Function ReturnMedSubtotal() as Integer Dim ThisValue as Integer = GroupMedTotal GroupMedTotal = 0 Return ThisValue End Function Basically CalcMedTotal is fed a SUM of a group, and maintains a running total of that sum. Then in the group total line I output ReturnMedSubtotal which is supposed to give me the accumulated total and reset it for the next group. This actually works great, EXCEPT - it is resetting the GroupMedTotal value on each page break. I don't have page breaks explicitly set, it's just the natural break in the SSRS viewer. And if I export the results to Excel everything works and looks correctly. If I output Code.GroupMedTotal on each group row, I see it count correctly, and then if a group spans multiple pages on the next page GroupMedTotal is reset and begins counting from zero again. Any help in what's going on or how to work around this? Thanks!

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  • Most readable way to write simple conditional check

    - by JRL
    What would be the most readable/best way to write a multiple conditional check such as shown below? Two possibilities that I could think of (this is Java but the language really doesn't matter here): Option 1: boolean c1 = passwordField.getPassword().length > 0; boolean c2 = !stationIDTextField.getText().trim().isEmpty(); boolean c3 = !userNameTextField.getText().trim().isEmpty(); if (c1 && c2 && c3) { okButton.setEnabled(true); } Option 2: if (passwordField.getPassword().length > 0 && !stationIDTextField.getText().trim().isEmpty() && !userNameTextField.getText().trim().isEmpty() { okButton.setEnabled(true); } What I don't like about option 2 is that the line wraps and then indentation becomes a pain. What I don't like about option 1 is that it creates variables for nothing and requires looking at two places. So what do you think? Any other options?

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