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• Installing PIL on Cygwin

  - by Dustin

  I've been struggling all morning to get PIL installed on Cygwin. The errors I get are not consistent with common errors I find using Google. Perhaps a linux guru can see an obvious problem in this output: $ python setup.py install running install running build running build_py running build_ext building '_imaging' extension gcc -fno-strict-aliasing -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -DHAVE_LIBZ -I/usr/include/freetype2 -IlibImaging -I/usr/include -I/usr/include/python2.5 -c _imaging.c -o build/temp.cygwin-1.7.2-i686-2.5/_imaging.o In file included from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/syslimits.h:7, from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/limits.h:11, from /usr/include/python2.5/Python.h:18, from _imaging.c:75: /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/limits.h:122:61: limits.h: No such file or directory In file included from _imaging.c:75: /usr/include/python2.5/Python.h:32:19: stdio.h: No such file or directory /usr/include/python2.5/Python.h:34:5: #error "Python.h requires that stdio.h define NULL." /usr/include/python2.5/Python.h:37:20: string.h: No such file or directory /usr/include/python2.5/Python.h:39:19: errno.h: No such file or directory /usr/include/python2.5/Python.h:41:20: stdlib.h: No such file or directory /usr/include/python2.5/Python.h:43:20: unistd.h: No such file or directory /usr/include/python2.5/Python.h:55:20: assert.h: No such file or directory In file included from /usr/include/python2.5/Python.h:57, from _imaging.c:75: /usr/include/python2.5/pyport.h:7:20: stdint.h: No such file or directory In file included from /usr/include/python2.5/Python.h:57, from _imaging.c:75: /usr/include/python2.5/pyport.h:89: error: parse error before "Py_uintptr_t" /usr/include/python2.5/pyport.h:89: warning: type defaults to `int' in declaration of `Py_uintptr_t' /usr/include/python2.5/pyport.h:89: warning: data definition has no type or storage class /usr/include/python2.5/pyport.h:90: error: parse error before "Py_intptr_t" /usr/include/python2.5/pyport.h:90: warning: type defaults to `int' in declaration of `Py_intptr_t' ... more lines like this

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• Noob - Cycle through stored names and skip blanks

  - by ActiveJimBob

  NOOB trying to make my code more efficient. On scroll button push, the function 'SetName' stores a number to integer 'iName' which is index against 5 names stored in memory. If a name is not set in memeory, it skips to the next. The code works, but takes up a lot of room. Any advice appreciated. Code: #include <string.h> int iName = 0; int iNewName = 0; BYTE GetName () { return iName; } void SetName (int iNewName) { while (iName != iNewName) { switch (byNewName) { case 1: if (strlen (memory.m_nameA) == 0) new_name++; else iName = iNewName; break; case 2: if (strlen (memory.m_nameB) == 0) new_name++; else iName = iNewName; break; case 3: if (strlen (memory.m_nameC) == 0) new_name++; else iName = iNewName; break; case 4: if (strlen (memory.m_nameD) == 0) new_name++; else iName = iNewName; break; case 5: if (strlen (memory.m_nameE) == 0) new_name++; else iName = iNewName; break; default: iNewName = 1; break; } // end of case } // end of loop } // end of SetName function void main () { while(1) { if (Button_pushed) SetName(GetName+1); } // end of infinite loop } // end of main

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• Create a new delegate class for each asynchronous image download?

  - by Charles S.

  First, I'm using an NSURLConnection to download JSON data from twitter. Then, I'm using a second NSURLConnection to download corresponding user avatar images (the urls to the images are parsed from the first data download). For the first data connection, I have my TwitterViewController set as the NSURLConnection delegate. I've created a separate class (ImageDownloadDelegate) to function as the delegate for a second NSURLConnection that handles the images. After the tweets are finished downloading, I'm using this code to get the avatars: for(int j=0; j<[self.tweets count]; j++){ ImageDownloadDelegate *imgDelegate = [[ImageDownloadDelegate alloc] init]; Tweet *myTweet = [self.tweets objectAtIndex:j]; imgDelegate.tweet = myTweet; imgDelegate.table = timeline; NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:myTweet.imageURL] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60]; imgConnection = [[NSURLConnection alloc] initWithRequest:request delegate:imgDelegate]; [imgDelegate release]; } So basically a new instance of the delegate class is created for each image that needs to be downloaded. Is this the best way to go about this? But then there's no way to figure out which image is associate with which tweet, correct? The algorithm works fine... I'm just wondering if I'm going about it the most efficient way.

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• Sparse (Pseudo) Infinite Grid Data Structure for Web Game

  - by Ming

  I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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• Django Querysets -- need a less expensive way to do this..

  - by rh0dium

  Hi all, I have a problem with some code and I believe it is because of the expense of the queryset. I am looking for a much less expensive (in terms of time) way to to this.. log.info("Getting Users") employees = Employee.objects.filter(is_active = True) log.info("Have Users") if opt.supervisor: if opt.hierarchical: people = getSubs(employees, " ".join(args)) else: people = employees.filter(supervisor__name__icontains = " ".join(args)) else: log.info("Filtering Users") people = employees.filter(name__icontains = " ".join(args)) | \ employees.filter(unix_accounts__username__icontains = " ".join(args)) log.info("Filtered Users") log.info("Processing data") np = [] for person in people: unix, p4, bugz = "No", "No", "No" if len(person.unix_accounts.all()): unix = "Yes" if len(person.perforce_accounts.all()): p4 = "Yes" if len(person.bugzilla_accounts.all()): bugz = "Yes" if person.cell_phone != "": exphone = fixphone(person.cell_phone) elif person.other_phone != "": exphone = fixphone(person.other_phone) else: exphone = "" np.append({ 'name':person.name, 'office_phone': fixphone(person.office_phone), 'position': person.position, 'location': person.location.description, 'email': person.email, 'functional_area': person.functional_area.name, 'department': person.department.name, 'supervisor': person.supervisor.name, 'unix': unix, 'perforce': p4, 'bugzilla':bugz, 'cell_phone': fixphone(exphone), 'fax': fixphone(person.fax), 'last_update': person.last_update.ctime() }) log.info("Have data") Now this results in a log which looks like this.. 19:00:55 INFO phone phone Getting Users 19:00:57 INFO phone phone Have Users 19:00:57 INFO phone phone Processing data 19:01:30 INFO phone phone Have data As you can see it's taking over 30 seconds to simply iterate over the data. That is way too expensive. Can someone clue me into a more efficient way to do this. I thought that if I did the first filter that would make things easier but seems to have no effect. I'm at a loss on this one. Thanks To be clear this is about 1500 employees -- Not too many!!

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• Switch/case without break inside DllMain

  - by Sherwood Hu

  I have a Dllmain that allocates Thread local storage when a thread attaches to this DLL. Code as below: BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) { LPVOID lpvData; BOOL fIgnore; switch (ul_reason_for_call) { case DLL_PROCESS_ATTACH: onProcessAttachDLL(); // Allocate a TLS index. if ((dwTlsIndex = TlsAlloc()) == TLS_OUT_OF_INDEXES) return FALSE; // how can it jump to next case??? case DLL_THREAD_ATTACH: // Initialize the TLS index for this thread. lpvData = (LPVOID) LocalAlloc(LPTR, MAX_BUFFER_SIZE); if (lpvData != NULL) fIgnore = TlsSetValue(dwTlsIndex, lpvData); break; ... } I know that for the main thread, the DLL_THREAD_ATTACH is not entered, as per Microsoft Documentation. However, the above code worked. I am using VC2005. When I entered the debugger, I saw that after it entered DLL_THREAD_ATTACH case when ul_reason_for_call = 1! How can that happen? If I add `break' at the end of DLL_PROCESS_ATTACH block, the DLL failed to work. How can this happen?

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• Trouble with custom WPF Panel-derived class

  - by chaiguy

  I'm trying to write a custom Panel class for WPF, by overriding MeasureOverride and ArrangeOverride but, while it's mostly working I'm experiencing one strange problem I can't explain. In particular, after I call Arrange on my child items in ArrangeOverride after figuring out what their sizes should be, they aren't sizing to the size I give to them, and appear to be sizing to the size passed to their Measure method inside MeasureOverride. Am I missing something in how this system is supposed to work? My understanding is that calling Measure simply causes the child to evaluate its DesiredSize based on the supplied availableSize, and shouldn't affect its actual final size. Here is my full code (the Panel, btw, is intended to arrange children in the most space-efficient manner, giving less space to rows that don't need it and splitting remaining space up evenly among the rest--it currently only supports vertical orientation but I plan on adding horizontal once I get it working properly): protected override Size MeasureOverride( Size availableSize ) { foreach ( UIElement child in Children ) child.Measure( availableSize ); return availableSize; } protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize ) { double extraSpace = 0.0; var sortedChildren = Children.Cast<UIElement>().OrderBy<UIElement, double>( new Func<UIElement, double>( delegate( UIElement child ) { return child.DesiredSize.Height; } ) ); double remainingSpace = finalSize.Height; double normalSpace = 0.0; int remainingChildren = Children.Count; foreach ( UIElement child in sortedChildren ) { normalSpace = remainingSpace / remainingChildren; if ( child.DesiredSize.Height < normalSpace ) // if == there would be no point continuing as there would be no remaining space remainingSpace -= child.DesiredSize.Height; else { remainingSpace = 0; break; } remainingChildren--; } extraSpace = remainingSpace / Children.Count; double offset = 0.0; foreach ( UIElement child in Children ) { //child.Measure( new Size( finalSize.Width, normalSpace ) ); double value = Math.Min( child.DesiredSize.Height, normalSpace ) + extraSpace; child.Arrange( new Rect( 0, offset, finalSize.Width, value ) ); offset += value; } return finalSize; }

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• LINQ to SQL - How to efficiently do either an AND or an OR search for multiple criteria

  - by Dan Diplo

  I have an ASP.NET MVC site (which uses Linq To Sql for the ORM) and a situation where a client wants a search facility against a bespoke database whereby they can choose to either do an 'AND' search (all criteria match) or an 'OR' search (any criteria match). The query is quite complex and long and I want to know if there is a simple way I can make it do both without having to have create and maintain two different versions of the query. For instance, the current 'AND' search looks something like this (but this is a much simplified version): private IQueryable<SampleListDto> GetSampleSearchQuery(SamplesCriteria criteria) { var results = from r in Table where (r.Id == criteria.SampleId) && (r.Status.SampleStatusId == criteria.SampleStatusId) && (r.Job.JobNumber.StartsWith(criteria.JobNumber)) && (r.Description.Contains(criteria.Description)) select r; } I could copy this and replace the && with || operators to get the 'OR' version, but feel there must be a better way of achieving this. Does anybody have any suggestions how this can be achieved in an efficient and flexible way that is easy to maintain? Thanks.

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• What is the purpose of the s==NULL case for mbrtowc?

  - by R..

  mbrtowc is specified to handle a NULL pointer for the s (multibyte character pointer) argument as follows: If s is a null pointer, the mbrtowc() function shall be equivalent to the call: mbrtowc(NULL, "", 1, ps) In this case, the values of the arguments pwc and n are ignored. As far as I can tell, this usage is largely useless. If ps is not storing any partially-converted character, the call will simply return 0 with no side effects. If ps is storing a partially-converted character, then since '\0' is not valid as the next byte in a multibyte sequence ('\0' can only be a string terminator), the call will return (size_t)-1 with errno==EILSEQ. and leave ps in an undefined state. The intended usage seems to have been to reset the state variable, particularly when NULL is passed for ps and the internal state has been used, analogous to mbtowc's behavior with stateful encodings, but this is not specified anywhere as far as I can tell, and it conflicts with the semantics for mbrtowc's storage of partially-converted characters (if mbrtowc were to reset state when encountering a 0 byte after a potentially-valid initial subsequence, it would be unable to detect this dangerous invalid sequence). If mbrtowc were specified to reset the state variable only when s is NULL, but not when it points to a 0 byte, a desirable state-reset behavior would be possible, but such behavior would violate the standard as written. Is this a defect in the standard? As far as I can tell, there is absolutely no way to reset the internal state (used when ps is NULL) once an illegal sequence has been encountered, and thus no correct program can use mbrtowc with ps==NULL.

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• PHP Object References in Frameworks

  - by bigstylee

  Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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• How to replace characters in a java String?

  - by ManBugra

  I like to replace a certain set of characters of a string with a corresponding replacement character in an efficent way. For example: String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; String result = replaceChars("Gracišce", sourceCharacters , targetCharacters ); Assert.equals(result,"Gracisce") == true; Is there are more efficient way than to use the replaceAll method of the String class? My first idea was: final String s = "Gracišce"; String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; // preparation final char[] sourceString = s.toCharArray(); final char result[] = new char[sourceString.length]; final char[] targetCharactersArray = targetCharacters.toCharArray(); // main work for(int i=0,l=sourceString.length;i<l;++i) { final int pos = sourceCharacters.indexOf(sourceString[i]); result[i] = pos!=-1 ? targetCharactersArray[pos] : sourceString[i]; } // result String resultString = new String(result); Any ideas? Btw, the UTF-8 characters are causing the trouble, with US_ASCII it works fine.

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• Vertex Buffers in opengl

  - by JB

  I'm making a small 3d graphics game/demo for personal learning. I know d3d9 and quite a bit about d3d11 but little about opengl at the moment so I'm intending to abstract out the actual rendering of the graphics so that my scene graph and everything "above" it needs to know little about how to actually draw the graphics. I intend to make it work with d3d9 then add d3d11 support and finally opengl support. Just as a learning exercise to learn about 3d graphics and abstraction. I don't know much about opengl at this point though, and don't want my abstract interface to expose anything that isn't simple to implement in opengl. Specifically I'm looking at vertex buffers. In d3d they are essentially an array of structures, but looking at the opengl interface the equivalent seems to be vertex arrays. However these seem to be organised rather differently where you need a separate array for vertices, one for normals, one for texture coordinates etc and set the with glVertexPointer, glTexCoordPointer etc. I was hoping to be able to implement a VertexBuffer interface much like the the directx one but it looks like in d3d you have an array of structures and in opengl you need a separate array for each element which makes finding a common abstraction quite hard to make efficient. Is there any way to use opengl in a similar way to directx? Or any suggestions on how to come up with a higher level abstraction that will work efficiently with both systems?

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• ajax html vs xml/json responses - perfomance or other reasons

  - by pedalpete

  I've got a fairly ajax heavy site and some 3k html formatted pages are inserted into the DOM from ajax requests. What I have been doing is taking the html responses and just inserting the whole thing using jQuery. My other option is to output in xml (or possibly json) and then parse the document and insert it into the page. I've noticed it seems that most larger site do things the json/xml way. Google Mail returns xml rather than formatted html. Is this due to performance? or is there another reason to use xml/json vs just retrieving html? From a javascript standpoint, it would seem injecting direct html is simplest. In jQuery I just do this jQuery.ajax({ type: "POST", url: "getpage.php", data: requestData, success: function(response){ jQuery('div#putItHear').html(response); } with an xml/json response I would have to do jQuery.ajax({ type: "POST", url: "getpage.php", data: requestData, success: function(xml){ $("message",xml).each(function(id) { message = $("message",xml).get(id); $("#messagewindow").prepend(""+$("author",message).text()+ ": "+$("text",message).text()+ ""); }); } }); clearly not as efficient from a code standpoint, and I can't expect that it is better browser performance, so why do things the second way?

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• How to check if two records have a self-referencing relation?

  - by Machine

  Consider the following schema with users and their collegues (friends): Users User: columns: user_id: name: user_id as userId type: integer(8) unsigned: 1 primary: true autoincrement: true first_name: name: first_name as firstName type: string(45) notnull: true last_name: name: last_name as lastName type: string(45) notnull: true email: type: string(45) notnull: true unique: true relations: Collegues: class: User local: invitor foreign: invitee refClass: CollegueStatus equal: true onDelete: CASCADE onUpdate: CASCADE Join table: CollegueStatus: columns: invitor: type: integer(8) unsigned: 1 primary: true invitee: type: integer(8) unsigned: 1 primary: true status: type: enum(8) values: [pending, accepted, denied] default: pending notnull: true Now, let's say I two records, one for the user making a HTTP request (the logged in user), and one record for a user he wants to send a message to. I want to check if these users are collegues. Questions: Does Doctrine have any pre-build functionality to check if two records with with self-relations are related? If not, how would you write a method to check this? Where would you put said method? (In the User-class, UserTable-class etc) I could probably do something like this: public function (User $user1, User $user2) { // Ensure we load collegues if $user1 was fetched with DQL that // doesn't load this relation $collegues = $user1->get('Collegues'); $areCollegues = false; foreach($collegues as $collegue) { if($collegue['userId'] === $user2['userId']) { $areCollegues = true; break; } } return $areCollegues; } But this looks a neither efficient nor pretty. I just feel that it should be solved already for self-referencing relations to be nice to use.

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• EC2 persistence of machine

  - by Seagull

  I want to 'persist' my Amazon EC2 images. My scenario: I have a range of Windows and Linux machines Some machines are EBS backed, whereas others are S3 backed. I need to be able to persist a machine (put it to sleep), preferably keeping all settings active I had them when the machine was running. I need to be able to quickly wake up a machine from sleep [Ideally with an SLA of less than 2 min to turn-on, if such an SLA is available with Amazon]. Here's the stuff that confuses me: AWS allows me to put EBS backed machines to sleep, but not S3 backed. I believe I can put S3 machines into some sort of persistence mode. But this involves shutting down the machine, writing it to S3 storage and then recovering from there (not a real sleep mode, but at least I don't continue to get billed for CPU). S3 backing seems to take a long time to either writing a machine to disk, or to recover (turn on a machine). I can't tell immediately which machines are EBS backed and which are S3 backed? It seems like I can instantiate either type, but it's not immediately clear how Amazon decided whether a given machine should be EBS or S3 backed. Advice?

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• How to catch YouTube embed code and turn into URL

  - by Jonathan Vanasco

  I need to strip YouTube embed codes down to their URL only. This is the exact opposite of all but one question on StackOverflow. Most people want to turn the URL into an embed code. This question addresses the usage patttern I want, but is tied to a specific embed code's regex ( Strip YouTube Embed Code Down to URL Only ) I'm not familiar with how YouTube has offered embeds over the years - or how the sizes differ. According to their current site, there are 2 possible embed templates and a variety of options. If that's it, I can handle a regex myself -- but I was hoping someone had more knowledge they could share, so I could write a proper regex pattern that matches them all and not run into endless edge-cases. The full use case scenario : user enters content in web based wysiwig editor backend cleans out youtube & other embed codes; reformats approved embeds into an internal format as the text is all converted to markdown. on display, appropriate current template/code display for youtube or other 3rd party site is generated At a previous company, our tech-team devised a plan where YouTube videos were embedded by listing the URL only. That worked great , but it was in a CMS where everyone was trained. I'm trying to create a similar storage, but for user-generated-content.

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• Partially constructed object / Multi threading

  - by reto

  Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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• Return unordered list from hierarchical sql data

  - by Milan

  I have table with pageId, parentPageId, title columns. Is there a way to return unordered nested list using asp.net, cte, stored procedure, UDF... anything? Table looks like this: PageID ParentId Title 1 null Home 2 null Products 3 null Services 4 2 Category 1 5 2 Category 2 6 5 Subcategory 1 7 5 SubCategory 2 8 6 Third Level Category 1 ... Result should look like this: Home Products Category 1 SubCategory 1 Third Level Category 1 SubCategory 2 Category 2 Services Ideally, list should contain <a> tags as well, but I hope I can add it myself if I find a way to create <ul> list. EDIT 1: I thought that already there is a solution for this, but it seems that there isn't. I wanted to keep it simple as possible and to escape using ASP.NET menu at any cost, because it uses tables by default. Then I have to use CSS Adapters etc. Even if I decide to go down the "ASP.NET menu" route I was able to find only this approach: http://aspalliance.com/822 which uses DataAdapter and DataSet :( Any more modern or efficient way?

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• .Net lambda expression-- where did this parameter come from?

  - by larryq

  I'm a lambda newbie, so if I'm missing vital information in my description please tell me. I'll keep the example as simple as possible. I'm going over someone else's code and they have one class inheriting from another. Here's the derived class first, along with the lambda expression I'm having trouble understanding: class SampleViewModel : ViewModelBase { private ICustomerStorage storage = ModelFactory<ICustomerStorage>.Create(); public ICustomer CurrentCustomer { get { return (ICustomer)GetValue(CurrentCustomerProperty); } set { SetValue(CurrentCustomerProperty, value); } } private int quantitySaved; public int QuantitySaved { get { return quantitySaved; } set { if (quantitySaved != value) { quantitySaved = value; NotifyPropertyChanged(p => QuantitySaved); //where does 'p' come from? } } } public static readonly DependencyProperty CurrentCustomerProperty; static SampleViewModel() { CurrentCustomerProperty = DependencyProperty.Register("CurrentCustomer", typeof(ICustomer), typeof(SampleViewModel), new UIPropertyMetadata(ModelFactory<ICustomer>.Create())); } //more method definitions follow.. Note the call to NotifyPropertyChanged(p => QuantitySaved) bit above. I don't understand where the "p" is coming from. Here's the base class: public abstract class ViewModelBase : DependencyObject, INotifyPropertyChanged, IXtremeMvvmViewModel { public event PropertyChangedEventHandler PropertyChanged; protected virtual void NotifyPropertyChanged<T>(Expression<Func<ViewModelBase, T>> property) { MvvmHelper.NotifyPropertyChanged(property, PropertyChanged); } } There's a lot in there that's not germane to the question I'm sure, but I wanted to err on the side of inclusiveness. The problem is, I don't understand where the 'p' parameter is coming from, and how the compiler knows to (evidently?) fill in a type value of ViewModelBase from thin air? For fun I changed the code from 'p' to 'this', since SampleViewModel inherits from ViewModelBase, but I was met with a series of compiler errors, the first one of which statedInvalid expression term '=>' This confused me a bit since I thought that would work. Can anyone explain what's happening here?

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• Calling DI Container directly in method code (MVC Actions)

  - by fearofawhackplanet

  I'm playing with DI (using Unity). I've learned how to do Constructor and Property injection. I have a static container exposed through a property in my Global.asax file (MvcApplication class). I have a need for a number of different objects in my Controller. It doesn't seem right to inject these throught the constructor, partly because of the high quantity of them, and partly because they are only needed in some Actions methods. The question is, is there anything wrong with just calling my container directly from within the Action methods? public ActionResult Foo() { IBar bar = (Bar)MvcApplication.Container.Resolve(IBar); // ... Bar uses a default constructor, I'm not actually doing any // injection here, I'm just telling my conatiner to give me Bar // when I ask for IBar so I can hide the existence of the concrete // Bar from my Controller. } This seems the simplest and most efficient way of doing things, but I've never seen an example used in this way. Is there anything wrong with this? Am I missing the concept in some way?

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• Python - Checking for membership inside nested dict

  - by victorhooi

  heya, This is a followup questions to this one: http://stackoverflow.com/questions/2901422/python-dictreader-skipping-rows-with-missing-columns Turns out I was being silly, and using the wrong ID field. I'm using Python 3.x here. I have a dict of employees, indexed by a string, "directory_id". Each value is a nested dict with employee attributes (phone number, surname etc.). One of these values is a secondary ID, say "internal_id", and another is their manager, call it "manager_internal_id". The "internal_id" field is non-mandatory, and not every employee has one. (I've simplified the fields a little, both to make it easier to read, and also for privacy/compliance reasons). The issue here is that we index (key) each employee by their directory_id, but when we lookup their manager, we need to find managers by their "internal_id". Before, when employee.keys() was a list of internal_ids, I was using a membership check on this. Now, the last part of my if statement won't work, since the internal_ids is part of the dict values, instead of the key itself. def lookup_supervisor(manager_internal_id, employees): if manager_internal_idis not None and manager_internal_id!= "" and manager_internal_id in employees.keys(): return (employees[manager_internal_id]['mail'], employees[manager_internal_id]['givenName'], employees[manager_internal_id]['sn']) else: return ('Supervisor Not Found', 'Supervisor Not Found', 'Supervisor Not Found') So the first question is, how do I check whether the manager_internal_id is present in the dict's values. I've tried substituting employee.keys() with employee.values(), that didn't work. Also, I'm hoping for something a little more efficient, not sure if there's a way to get a subset of the values, specifically, all the entries for employees[directory_id]['internal_id']. Hopefully there's some Pythonic way of doing this, without using a massive heap of nested for/if loops. My second question is, how do I then cleanly return the required employee attributes (mail, givenname, surname etc.). My for loop is iterating over each employee, and calling lookup_supervisor. I'm feeling a bit stupid/stumped here. def tidy_data(employees): for directory_id, data in employees.items(): # We really shouldnt' be passing employees back and forth like this - hmm, classes? data['SupervisorEmail'], data['SupervisorFirstName'], data['SupervisorSurname'] = lookup_supervisor(data['manager_internal_id'], employees) Thanks in advance =), Victor

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• Tree data in MySql database table

  - by Robert Koritnik

  I have a table that uses Adjacency list model for hierarchy storage. My most relevant columns in this table are therefore: ItemId // is auto_increment ParentId Level ParentTrail // in the form of "parentId/../parentId/itemId" then I created a before insert tigger, that populates columns Level and ParentTrail. Since the last column also includes current item's ID I had to use a trick in my trigger because auto_increment columns are not available in the before insert trigger. So I get that value from the information_schema.tables table. All works fine, until I try to write an update trigger, that would update my item and its descendants when the item changes its parent (ParentId has changed). But I can't make an update on my table inside the update trigger. All I can do is to change current record's values but not other's. I could use a separate table for hierarchy data, but that would mean that I would also have to create a view that would combine these two tables (1:1 relation) and I would like to avoid this is at all possible. Is there a way to have all these in the same table so that these fields (Level and ParetTrail) set/update themselves automagically using triggers?

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• Most cost effective way to target multiple mobile platforms

  - by niidto

  Hi I have been given the tasks of speccing a mobile application, which will need to run on approx. 1000 devices. These devices already exist, and consist of iPhones, BlackBerrys, Androids, Windows Mobile and Netbooks. The application will have simple reporting capability, and a collection of forms. Anyway, the obvious solution would be to develop some browser based solution, although given the occasionally connected nature of the devices, there's a potential for data to get lost / not saved. So instead of creating a complex application for each platform, I was thinking we could build what is effectively a form generator, with basic offline storage capability (text files), designed to run on each device, and have the device generate a form, based on for example an XML file that it could request from a server somewhere, resulting in minimal specialist development costs, and the ability to run most of the logic from the server end, with the devices being dumb clients that render forms and upload the data when there is an available connection. Anyway, my question summarised is, how have you made the decision on supporting multiple devices for your application. Is this always an unavoidable problem, and you just have to make the call to support 1 or 2, or pay for developers to write code for each platform, or alternatively supply pre-installed devices to the company? Many thanks James

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• handling large arrays with array_diff

  - by bigmac

  I have been trying to compare two arrays. Using array_intersect presents no problems. When using array_diff and arrays with ~5,000 values, it works. When I get to ~10,000 values, the script dies when I get to array_diff. Turning on error_reporting did not produce anything. I tried creating my own array_diff function: function manual_array_diff($arraya, $arrayb) { foreach ($arraya as $keya => $valuea) { if (in_array($valuea, $arrayb)) { unset($arraya[$keya]); } } return $arraya; } source: http://stackoverflow.com/questions/2479963/how-does-array-diff-work I would expect it to be less efficient that than the official array_diff, but it can handle arrays of ~10,000. Unfortunately, both array_diffs fail when I get to ~15,000. I tried the same code on a different machine and it runs fine, so it's not an issue with the code or PHP. There must be some limit set somewhere on that particular server. Any idea how I can get around that limit or alter it or just find out what it is?

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• Point data structure for a sketching application

  - by bebraw

  I am currently developing a little sketching application based on HTML5 Canvas element. There is one particular problem I haven't yet managed to find a proper solution for. The idea is that the user will be able to manipulate existing stroke data (points) quite freely. This includes pushing point data around (ie. magnet tool) and manipulating it at whim otherwise (ie. altering color). Note that the current brush engine is able to shade by taking existing stroke data in count. It's a quick and dirty solution as it just iterates the points in the current stroke and checks them against a distance rule. Now the problem is how to do this in a nice manner. It is extremely important to be able to perform efficient queries that return all points within given canvas coordinate and radius. Other features, such as space usage, should be secondary to this. I don't mind doing some extra processing between strokes while the user is not painting. Any pointers are welcome. :)

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