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• How to delete duplicate/aggregate rows faster in a file using Java (no DB)

  - by S. Singh

  I have a 2GB big text file, it has 5 columns delimited by tab. A row will be called duplicate only if 4 out of 5 columns matches. Right now, I am doing dduping by first loading each coloumn in separate List , then iterating through lists, deleting the duplicate rows as it encountered and aggregating. The problem: it is taking more than 20 hours to process one file. I have 25 such files to process. Can anyone please share their experience, how they would go about doing such dduping? This dduping will be a throw away code. So, I was looking for some quick/dirty solution, to get job done as soon as possible. Here is my pseudo code (roughly) Iterate over the rows i=current_row_no. Iterate over the row no. i+1 to last_row if(col1 matches //find duplicate && col2 matches && col3 matches && col4 matches) { col5List.set(i,get col5); //aggregate } Duplicate example A and B will be duplicate A=(1,1,1,1,1), B=(1,1,1,1,2), C=(2,1,1,1,1) and output would be A=(1,1,1,1,1+2) C=(2,1,1,1,1) [notice that B has been kicked out]

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• MySQL - What is wrong with this query or my database? Terrible performance.

  - by Moss

  SELECT * from `employees` a LEFT JOIN (SELECT phone1 p1, count(*) c, FROM `employees` GROUP BY phone1) b ON a.phone1 = b.p1; I'm not sure if it is this query in particular that has the problem. I have been getting terrible performance in general with this database. The table in question has 120,000 rows. I have tried this particular query remotely and locally with the MyISAM and InnoDB engines, with different types of joins, and with and without an index on phone1. I can get this to complete in about 4 minutes on a 10,000 row table successfully but performance drops exponentially with larger tables. Remotely it will lose connection to the server and locally it brings my system to its knees and seems to go on forever. This query is only a smaller step I was trying to do when a larger query couldn't complete. Maybe I should explain the whole scenario. I have one big flat ugly table that lists a bunch of people and their contact info and the info of the companies they work for. I'm trying to normalize the database and intelligently determine which phone numbers apply to individual people and which apply to an office location. My reasoning is that if a phone number occurs multiple times and the number of occurrence equals the number of times that the street address it is attached to occurs then it must be an office number. So the first step is to count each phone number grouping by phone number. Normally if you just use COUNT()...GROUP BY it will only list the first record it finds in that group so I figured I have to join the full table to the count table where the phone number matches. This does work but as I said I can't successfully complete it on any table much larger than 10,000 rows. This seems pathetic and this doesn't seem like a crazy query to do. Is there a better way to achieve what I want or do I have to break my large table into 12 pieces or is there something wrong with the table or db?

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• Help me plan larger Qt project

  - by Pirate for Profit

  I'm trying to create an automated task management system for our company, because they pay me to waste my time. New users will create a "profile", which will store all the working data (I guess serialize everything into xml rite?). A "profile" will contain many different tasks. Tasks are basically just standard computer janitor crap such as moving around files, reading/writing to databases, pinging servers, etc.). So as you can see, a task has many different jobs they do, and also that tasks should run indefinitely as long as the user somehow generates "jobs" for them. There should also be a way to enable/disable (start/pause) tasks. They say create the UI first so... I figure the best way to represent this is with a list-view widget, that lists all the tasks in the profile. Enabled tasks will be bold, disabled will be then when you double-click a task, a tab in the main view opens with all the settings, output, errors,. You can right click a task in the list-view to enable/disable/etc. So each task will be a closable tab, but when you close it just hides. My question is: should I extend from QAction and QTabWidget so I can easily drop tasks in and out of my list-view and tab bar? I'm thinking some way to make this plugin-based, since a lot of the plugins may share similar settings (like some of the same options, but different infos are input). Also, what's the best way to set up threading for this application?

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• Delphi - Clean TListBox Items

  - by Brad

  I want to clean a list box by checking it against two other list boxes. Listbox1 would have the big list of items Listbox2 would have words I want removed from listbox1 Listbox3 would have mandatory words that have to exist for it to remain in listbox1 Below is the code I've got so far for this, it's VERY slow with large lists. // not very efficient Function checknegative ( instring : String; ListBox : TListBox ) : Boolean; Var i : Integer; Begin For I := listbox.Items.Count - 1 Downto 0 Do Begin If ExistWordInString ( instring, listbox.Items.Strings [i], [soWholeWord, soDown] ) = True Then Begin result := True; //True if in list, False if not. break; End Else Begin result := False; End; End; result:=false; End; Function ExistWordInString ( aString, aSearchString : String; aSearchOptions : TStringSearchOptions ) : Boolean; Var Size : Integer; Begin Size := Length ( aString ); If SearchBuf ( Pchar ( aString ), Size, 0, 0, aSearchString, aSearchOptions ) <> Nil Then Begin result := True; End Else Begin result := False; End; End;

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• Android CursorAdapters, ListViews and background threads

  - by MattC

  This application I've been working on has databases with multiple megabytes of data to sift through. A lot of the activities are just ListViews descending through various levels of data within the databases until we reach "documents", which is just HTML to be pulled from the DB(s) and displayed on the phone. The issue I am having is that some of these activities need to have the ability to search through the databases by capturing keystrokes and re-running the query with a "like %blah%" in it. This works reasonably quickly except when the user is first loading the data and when the user first enters a keystroke. I am using a ResourceCursorAdapter and I am generating the cursor in a background thread, but in order to do a listAdapter.changeCursor(), I have to use a Handler to post it to the main UI thread. This particular call is then freezing the UI thread just long enough to bring up the dreaded ANR dialog. I'm curious how I can offload this to a background thread totally so the user interface remains responsive and we don't have ANR dialogs popping up. Just for full disclosure, I was originally returning an ArrayList of custom model objects and using an ArrayAdapter, but (understandably) the customer pointed out it was bad memory-manangement and I wasn't happy with the performance anyways. I'd really like to avoid a solution where I'm generating huge lists of objects and then doing a listAdapter.notifyDataSetChanged/Invalidated() Here is the code in question: private Runnable filterDrugListRunnable = new Runnable() { public void run() { if (filterLock.tryLock() == false) return; cur = ActivityUtils.getIndexItemCursor(DrugListActivity.this); if (cur == null || forceRefresh == true) { cur = docDb.getItemCursor(selectedIndex.getIndexId(), filter); ActivityUtils.setIndexItemCursor(DrugListActivity.this, cur); forceRefresh = false; } updateHandler.post(new Runnable() { public void run() { listAdapter.changeCursor(cur); } }); filterLock.unlock(); updateHandler.post(hideProgressRunnable); updateHandler.post(updateListRunnable); } };

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• PHP While loop seperating unique categories from multiple 'Joined' tables

  - by Hob

  I'm pretty new to Joins so hope this all makes sense. I'm joining 4 tables and want to create a while loop that spits out results nested under different categories. My Tables categories id | category_name pages id | page_name | category *page_content* id | page_id | image_id images id | thumb_path My current SQL join <?php $all_photos = mysql_query(" SELECT * FROM categories JOIN pages ON pages.category = categories.id JOIN image_pages ON image_pages.page_id = pages.id JOIN images ON images.id = image_pages.image_id ");?> The result I want from a while loop I would like to get something like this.... Category 1 page 1 Image 1, image 2, image 3 page 2 Image 2, image 4 Category 2 page 3 image 1 page 4 image 1, image 2, image 3 I hope that makes sense. Each image can fall under multiple pages and each page can fall under multiple categories. at the moment I have 2 solutions, one which lists each category several times according to the the amount of pages inside them: eg. category 1, page 1, image 1 - category 1, page 1, image 2 etc One that uses a while loop inside another while loop inside another while loop, resulting in 3 sql queries. <?php while($all_page = mysql_fetch_array($all_pages)) { ?> <p><?=$all_page['page_name']?></p> <?php $all_images = mysql_query("SELECT * FROM images JOIN image_pages ON image_pages.page_id = " . $all_page['id'] . " AND image_pages.image_id = images.id"); ?> <div class="admin-images-block clearfix"> <?php while($all_image = mysql_fetch_array($all_images)) { ?> <img src="<?=$all_image['thumb_path']?>" alt="<?=$all_image['title']?>"/> <?php } ?> </div> <?php } } ?

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• Linq Select: Using a value from a list if available

  - by musefan

  I am going to use some basic stripped down examples to illustrate my problem. I have a class: class Item { int ID; bool Selected; } Now lets say I have two lists of the Item class: List<Item> ListA = GetListA(); List<Item> ListB = GetListB(); Now I want to create a third list that has all the items from ListB. The important thing is that if a match (same ID) if found in ListA then I want to use that Selected value, otherwise I want to keep the Selected value of the item that is in ListB. I am creating the third list as follows: List<Item> ListC = from item in ListB select new Item { ID = item.ID, Selected = item.Selected// <-- should use value form ListA if available }; Important: I don't want to seem ignorant, but I do not want to change the way ListC is created. By that I mean I want to use the "linq select" method, and I want to use a "one liner" that assigns the Selected value... I know there are other ways to create the list which will work just fine, but then I won't learn anything new. I have tried a couple of things so far... I know this will work, but I don't want to query ListA twice: Selected = ListA.Any(x => x.ID == item.ID) ? ListA.First(x => x.ID == item.ID).Selected : item.Selected and I also tried using DeafultIfEmpty but I don't think that is the right think for this situation... because it didn't work, and it seems it is more use if ListA was empty (which I don't care about)

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• C++: Copy contructor: Use Getters or access member vars directly?

  - by cbrulak

  Have a simple container class: public Container { public: Container() {} Container(const Container& cont) //option 1 { SetMyString(cont.GetMyString()); } //OR Container(const Container& cont) //option 2 { m_str1 = cont.m_str1; } public string GetMyString() { return m_str1;} public void SetMyString(string str) { m_str1 = str;} private: string m_str1; } So, would you recommend this method or accessing the member variables directly? In the example, all code is inline, but in our real code there is no inline code. Update (29 Sept 09): Some of these answers are well written however they seem to get missing the point of this question: this is simple contrived example to discuss using getters/setters vs variables initializer lists or private validator functions are not really part of this question. I'm wondering if either design will make the code easier to maintain and expand. Some ppl are focusing on the string in this example however it is just an example, imagine it is a different object instead. I'm not concerned about performance. we're not programming on the PDP-11

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• Is it okay for multiple objects to retain the same object in Objective-C/Cocoa?

  - by Andrew Arrow

  Say I have a tableview class that lists 100 Foo objects. It has: @property (nonatomic, retain) NSMutableArray* fooList; and I fill it up with Foos like: self.fooList = [NSMutableArray array]; while (something) { Foo* foo = [[Foo alloc] init]; [fooList addObject:foo]; [foo release]; } First question: because the NSMutableArray is marked as retain, that means all the objects inside it are retained too? Am I correctly adding the foo and releasing the local copy after it's been added to the array? Or am I missing a retain call? Then if the user selects one specific row in the table and I want to display a detail Foo view I call: FooView* localView = [[FooView alloc] initWithFoo:[self.fooList objectAtIndex:indexPath.row]]; [self.navigationController pushViewController:localView animated:YES]; [localView release]; Now the FooView class has: @property (nonatomic, retain) Foo* theFoo; so now BOTH the array is holding on to that Foo as well as the FooView. But that seems okay right? When the user hits the back button dealloc will be called on FooView and [theFoo release] will be called. Then another back button is hit and dealloc is called on the tableview class and [fooList release] is called. You might argue that the FooView class should have: @property (nonatomic, assign) Foo* theFoo; vs. retain. But sometimes the FooView class is called with a Foo that's not also in an array. So I wanted to make sure it was okay to have two objects holding on to the same other object.

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• How to handle build rule with unknown targets in OMake when target list generator is built

  - by Michael E

  I have a project which uses OMake for its build system, and I am trying to handle a rather tough corner case. I have some definition files and a tool which can take these definition files and create GraphViz files. There are two problems, though: Each definition file can produce multiple graphs, and the list of graphs it can produce is encoded in the file. My dump tool does have a -list option which lists all the graphs a definition file will produce. This dump tool is built in the source tree. I want this list available in the OMakefile so I can use other rules to convert the DOT files to SVG, and have a phony target depend on all the SVGs (goal: a single build command which builds SVG descriptions of all my graphs). If I only had the first problem, it would be easy - I would run the tool to build a list, and then use that list to build a target which invokes the dumper to output the GraphViz files. However, I am rather stuck on forcing the dump tool to be built before it is needed. If this were make, I would just run make recursively to build the dump tool. OMake does not allow recursive invocation, however, and the build function is only usable from osh. Any suggestions for a good solution to this problem?

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• Convert List to Double Array by LINQ (C#3.0)

  - by Newbie

  I have two lists x1 and x2 of type double List<double> x1 = new List<double> { 0.0330, -0.6463}; List<double> x2 = new List<double> { -0.2718, -0.2240}; I am using the below function to convert it to double array List<List<double>> xData = new List<List<double>> { x1, x2 }; double[,] xArray = new double[xData.Count, xData[0].Count]; for (int i = 0; i < xData.Count; i++) { for (int j = 0; j < xData[0].Count; j++) { xArray[i, j] = xData[i][j]; } } Is it possible to do the same stuff (i.e. the function that is converting List to array) by using Linq. Using : (C#3.0) & Framework - 3.5 I want to do this by using Linq because I am learning it but not have sufficient knowledge to write that. Thanks Convert List to Double Array by LINQ (C#3.0)

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• Once an HTML document has a manifest (cache.manifest), how can you remove it?

  - by Michael F

  It seems that once you have a manifest entry, a la: <html manifest="cache.manifest"> Then that page (the master entry in the cache) will always be cached (at least by Safari) until the user does something to remove the cache, even if you later remove the manifest attribute from the html tag and update the manifest (by changing something within it), forcing the master entry to be reloaded along with everything else. In other words, if you have: index.html (with manifest defined) file1.js (referenced in manifest) file2.js (referenced in manifest) cache.manifest (lists the two js files) -- removing the manifest entry from index.html and modifying the manifest (so it gets expired by the browser and all content reloaded) will not stop this page from behaving as if it's still fully cached. If you view source on index.html you won't see the manifest listed anymore, but the browser will still request only the cache.manifest file, and unless that file's content is changed, no other changes to any files will be shown to the user. It seems like a pretty glaring bug, and it's present on iOS as well as Mac versions of Safari. Has anyone found a way of resetting the page and getting rid of the cache without requiring user intervention?

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• Concrete examples of state sharing between multiple viewmodels (WPF MVVM)

  - by JohnMetta

  I have a WPF/Entity Framework (4.0) project with many objects. I'd like to build the application so that that I can have object selection state shared across viewmodels. For Example: We have Cars, Drivers, Passengers, and Cargo classes. We also have UserControls for CarList, DriverList, etc. and editor windows for CarEditor, DriverEditor, etc. Furthermore, we have viewmodels for all of these (CarListViewModel, DriverListViewModel, CargoEditorViewModel, etc). This all composes a dockable interface where the user can have multiple object lists, editors, and viewers open. What I want is a concrete code example of how to wireup multiple viewmodels so that selecting a car in the CarList will cause that car to go live in the CarEditorView, but also be selected in any other view for which the context is valid (such as a DriverByCarView- or just DriverList if there is a filter predicate). There are a number of suggestions and discussions based on this question. The two methods that seem to dominate are: 3018307: Discusses state sharing by mentioning a messaging subsystem 1159035: Discusses state sharing by using an enclosing viewmodel Is one of these approaches better than the other? Does anyone have a concrete example of either/both of these methods in the form of a write-up or small code project? I'm still learning WPF, so pointers to entry points for reading API fundamentals are appreciated, but looking at code examples is where I usually go. Thanks In case anyone is interested, here are some other similar discussions: 3816961: Discusses returning multiple viewmodels depending on object type (i.e. a collection of arbitrary types adhering to a specific interface) 1928130: Discusses whether it is a good idea to aggregate viewmodels as properties of other viewmodels (e.g. a MainWindow viewmodel composed of panel viewmodels) 1120061: Essentially discusses whether to have use a viewmodel-per-model strategy or a viewmodel-per-view-element strategy. 4244222: Discusses whether or not to nest the viewmodels when using a nested object hierarchy. 4429708: Discusses sharing collections between viewmodels directly, but doesn't go into detail. List item: Discusses managing multiple selections within a single viewmodel.

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• How to make cycle over cycles in Java?

  - by Roman

  I would like to make a cycle over the following elements: [1,2,11,12,21,22,111,112,121,122,....,222222] or for example [1,2,3,11,12,13,21,22,23,31,32,33,111,112,113,... 333333333] How can I make it in Java? In my particular case I use 4 digits (1,2,3,4) and the length of the last number can be from 1 to 10. I managed to do it in Python and PHP. In the first case I used list over lists. I started from [[1],[2],] then for every element of the list I added 1 and 2, so I got [[1,1],[1,2],[2,1],[2,2]] and so on: nchips = sum(chips) traj = [[]] last = [[]] while len(last[0]) < nchips: newlast = [] for tr in last: for d in [1,2,3,4]: newlast.append(tr + [d]) last = newlast traj += last When I did it in PHP I used number with base 3. But it was a tricky and non elegant solution. for ($i=-1; $i<=$n; $i+=1) { if ($i>-1) { $n5 = base_convert($i,10,5); $n5_str = strval($n5); $tr = array(); $found = 0; for ($j=0; $j<strlen($n5_str); $j+=1) { $k = $n5_str[$j]; if ($k==0) { $found = 1; break; } array_push($tr,$k); } if ($found==1) continue; } else { $tr = array(); } } Can it be done easily in Java?

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• String comparison in Python: is vs. ==

  - by Coquelicot

  I noticed a Python script I was writing was acting squirrelly, and traced it to an infinite loop, where the loop condition was "while line is not ''". Running through it in the debugger, it turned out that line was in fact ''. When I changed it to != rather than 'is not', it worked fine. I did some searching, and found this question, the top answer to which seemed to be just what I needed. Except the answer it gave was counter to my experience. Specifically, the answerer wrote: For all built-in Python objects (like strings, lists, dicts, functions, etc.), if x is y, then x==y is also True. I double-checked the type of the variable, and it was in fact of type str (not unicode or something). Is his answer just wrong, or is there something else afoot? Also, is it generally considered better to just use '==' by default, even when comparing int or Boolean values? I've always liked to use 'is' because I find it more aesthetically pleasing and pythonic (which is how I fell into this trap...), but I wonder if it's intended to just be reserved for when you care about finding two objects with the same id.

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• Excel VBA creating a new column with formula

  - by Amatya

  I have an excel file with a column which has date data. I want the user to input a date of their choosing and then I want to create a new column that lists the difference in days between the two dates. The Macro that I have is working but I have a few questions and I would like to make it better. Link to MWE small data file is here. The user input date was 9/30/2013, which I stored in H20 Macro: Sub Date_play() Dim x As Date Dim x2 As Date Dim y As Variant x = InputBox(Prompt:="Please enter the Folder Report Date. The following formats are acceptable: 4 1 2013 or April 1 2013 or 4/1/2013") x2 = Range("E2") y = DateDiff("D", x2, x) MsgBox y 'Used DateDiff above and it works but I don't know how to use it to fill a column or indeed a cell. Range("H20").FormulaR1C1 = x Range("H1").FormulaR1C1 = "Diff" Range("H2").Formula = "=DATEDIF(E2,$H$20,""D"")" Range("H2").AutoFill Destination:=Range("H2:H17") Range("H2:H17").Select End Sub Now, could I have done this without storing the user input date in a particular cell? I would've preferred to use the variable "x" in the formula but it wasn't working for me. I had to store the user input in H20 and then use $H$20. What's the difference between the function Datedif and the procedure DateDiff? I am able to use the procedure DateDiff in my macro but I don't know how to use it to fill out my column. Is one method better than the other? Is there a better way to add columns to the existing sheet, where the columns include some calculations involving existing data on the sheet and some user inputs? There are tons of more complicated calculations I want to do next. Thanks

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• Entity Framework Validation & usage

  - by kmsellers

  I'm aware there is an AssociationChanged event, however, this event fires after the association is made. There is no AssociationChanging event. So, if I want to throw an exception for some validation reason, how do I do this and get back to my original value? Also, I would like to default values for my entity based on information from other entities but do this only when I know the entitiy is instanced for insertion into the database. How do I tell the difference between that and the object getting instanced because it is about to be populated based on existing data? Am I supposed to know? Is that considiered business logic that should be outside of my entity business logic? If that's the case, then should I be designing controller classes to wrap all these entities? My concern is that if I deliver back an entity, I want the client to get access to the properties, but I want to retain tight control over validations on how they are set, defaulted, etc. Every example I've seen references context, which is outside of my enity partial class validation, right? BTW, I looked at the EFPocoAdapter and for the life of me cannot determine how to populate lists of from within my POCO class... anyone know how I get to the context from a EFPoco Class?

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• Compressing a database to a single file?

  - by Assimilater

  Hi all. In my contact manager program I have been storing information by reading and writing comma delimited files for each individual contact, and storing notes in a file for each note, and I'm wondering how I could go about shrinking them all into one file effectively. I have attempted using data entry tools in the visual studio toolbox and template class, though I have never quite figured out how to use them. What would be especially convenient is if I could store data as data type IOwner (a class I created) as opposed to strings. I'd also need to figure out how to tell the program what to do when a file is opened (I've noticed in the properties how to associate a file type with the program though am not sure how to tell it what to do when it's opened). Edit: How about rephrasing the question: I have a class IContact with various properties some of them being lists of other class objects. I have a public list of IContact. Can I write Contacts as List(Of IContact) to a file as opposed to a bunch of strings? Second part of the question: I have associated .cms files with my program. But if a user opens the file, what code should the program run through in an attempt to deal with the file? This file is going to contain data that the program needs to read, how do I tell it to read a file when the program is opened vicariously because the file was opened? Does this make the question clearer?

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• When is it safe to use a broken hash function?

  - by The Rook

  It is trivial to use a secure hash function like SHA256 and continuing to use md5 is reckless behavior. However, there are some complexities to hash function vulnerabilities that I would like to better understand. Collisions have been generated for md4 and md5. According to NIST md5() is not a secure hash function. It only takes 2^39th operations to generate a collision and should never be used for passwords. However SHA1 is vulnerable to a similar collision attack in which a collision can be found in 2^69 operations, where as brute force is 2^80th. No one has generated a sha1 collision and NIST still lists sha1 as a secure message digest function. So when is it safe to use a broken hash function? Even though a function is broken it can still be "big enough". According to Schneier a hash function vulnerable to a collsion attack can still be used as an HMAC. I believe this is because the security of an HMAC is Dependant on its secret key and a collision cannot be found until this key is obtained. Once you have the key used in a HMAC its already broken, so its a moot point. What hash function vulnerabilities would undermine the security of an HMAC? Lets take this property a bit further. Does it then become safe to use a very weak message digest like md4 for passwords if a salt is perpended to the password? Keep in mind the md4 and md5 attacks are prefixing attacks, and if a salt is perpended then an attacker cannot control the prefix of the message. If the salt is truly a secret, and isn't known to the attacker, then does it matter if its a appended to the end of the password? Is it safe to assume that an attacker cannot generate a collision until the entire message has been obtained? Do you know of other cases where a broken hash function can be used in a security context without introducing a vulnerability? (Please post supporting evidence because it is awesome!)

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• Compare Properties automatically

  - by juergen d

  I want to get the names of all properties that changed for matching objects. I have these (simplified) classes: public enum PersonType { Student, Professor, Employee } class Person { public string Name { get; set; } public PersonType Type { get; set; } } class Student : Person { public string MatriculationNumber { get; set; } } class Subject { public string Name { get; set; } public int WeeklyHours { get; set; } } class Professor : Person { public List<Subject> Subjects { get; set; } } Now I want to get the objects where the Property values differ: List<Person> oldPersonList = ... List<Person> newPersonList = ... List<Difference> = GetDifferences(oldPersonList, newPersonList); public List<Difference> GetDifferences(List<Person> oldP, List<Person> newP) { //how to check the properties without casting and checking //for each type and individual property?? //can this be done with Reflection even in Lists?? } In the end I would like to have a list of Differences like this: class Difference { public List<string> ChangedProperties { get; set; } public Person NewPerson { get; set; } public Person OldPerson { get; set; } } The ChangedProperties should contain the name of the changed properties.

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• I have a bunch of template parameters that I want to hide from my users. How can I do this?

  - by Alex

  I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

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• Fast find object by string property

  - by Andrew Kalashnikov

  Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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• Custom PHP Framework Feedback

  - by Jascha

  I've been learning OOP programming for about a year and a half now and have developed a fairly standard framework to which I generally abide by. I'd love some feedback or input on how I might improve some functionality or if there are some things I'm overlooking. VIEW MODE 1) Essentially everything starts at the Index.php page. The first thing I do is require my "packages.php" file that is basically a config file that imports all of the classes and function lists I'll be using. 2) I have no direct communication between my index.php file and my classes, what I've done is "pretty them up" with my viewfunctions.php file which is essentially just a conduit to the classes so that in my html I can write <?php get_title('page'); ?> instead of <?php echo $pageClass->get_title('page'); ?> Plus, I can run a couple small booleans and what not in the view function script that can better tailor the output of the class. 3) Any information brought in via the database is started from it's corresponding class that has direct communication with the database class, the only class that is allowed direct to communicate with the database (allowed in the sense that I run all of my queries with custom class code). INPUT MODE 1) Any user input is sent to my userFunctions.php. 2) My security class is then instantiated where I send whatever user input that has been posted for verification and validation. 3) If the input passes my security check, I then pass it to my DB class for input into my Database. FEEDBACK I'm wondering if there are any glaringly obvious pitfalls to the general structure, or ways I can improve this. Thank you in advance for your input. I know there is real no "right" answer for this, but I imagine a couple up votes would be in order for some strong advice regarding building frameworks. -J

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• Extended slice that goes to beginning of sequence with negative stride

  - by recursive

  Bear with me while I explain my question. Skip down to the bold heading if you already understand extended slice list indexing. In python, you can index lists using slice notation. Here's an example: >>> A = list(range(10)) >>> A[0:5] [0, 1, 2, 3, 4] You can also include a stride, which acts like a "step": >>> A[0:5:2] [0, 2, 4] The stride is also allowed to be negative, meaning the elements are retrieved in reverse order: >>> A[5:0:-1] [5, 4, 3, 2, 1] But wait! I wanted to see [4, 3, 2, 1, 0]. Oh, I see, I need to decrement the start and end indices: >>> A[4:-1:-1] [] What happened? It's interpreting -1 as being at the end of the array, not the beginning. I know you can achieve this as follows: >>> A[4::-1] [4, 3, 2, 1, 0] But you can't use this in all cases. For example, in a method that's been passed indices. My question is: Is there any good pythonic way of using extended slices with negative strides and explicit start and end indices that include the first element of a sequence? This is what I've come up with so far, but it seems unsatisfying. >>> A[0:5][::-1] [4, 3, 2, 1, 0]

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