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  • Spring Data Neo4J @Indexed(unique = true) not working

    - by Markus Lamm
    I'm new to Neo4J and I have, probably an easy question. There're NodeEntitys in my application, a property (name) is annotated with @Indexed(unique = true) to achieve the uniqueness like I do in JPA with @Column(unique = true). My problem is, that when I persist an entity with a name that already exists in my graph, it works fine anyway. But I expected some kind of exception here...?! Here' s an overview over basic my code: @NodeEntity public abstract class BaseEntity implements Identifiable { @GraphId private Long entityId; ... } public class Role extends BaseEntity { @Indexed(unique = true) private String name; ... } public interface RoleRepository extends GraphRepository<Role> { Role findByName(String name); } @Service public class RoleServiceImpl extends BaseEntityServiceImpl<Role> implements { private RoleRepository repository; @Override @Transactional public T save(final T entity) { return getRepository().save(entity); } } And this is my test: @Test public void testNameUniqueIndex() { final List<Role> roles = Lists.newLinkedList(service.findAll()); final String existingName = roles.get(0).getName(); Role newRole = new Role.Builder(existingName).build(); newRole = service.save(newRole); } That's the point where I expect something to go wrong! How can I ensure the uniqueness of a property, without checking it for myself?? THANKS IN ADVANCE FOR ANY IDEAS!! P.S.: I'm using neo4j 1.8.M07, spring-data-neo4j 2.1.0.BUILD-SNAPSHOT and Spring 3.1.2.RELEASE.

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  • How can I introduce a regex action to match the first element in a Catalyst URI ?

    - by RET
    Background: I'm using a CRUD framework in Catalyst that auto-generates forms and lists for all tables in a given database. For example: /admin/list/person or /admin/add/person or /admin/edit/person/3 all dynamically generate pages or forms as appropriate for the table 'person'. (In other words, Admin.pm has actions edit, list, add, delete and so on that expect a table argument and possibly a row-identifying argument.) Question: In the particular application I'm building, the database will be used by multiple customers, so I want to introduce a URI scheme where the first element is the customer's identifier, followed by the administrative action/table etc: /cust1/admin/list/person /cust2/admin/add/person /cust2/admin/edit/person/3 This is for "branding" purposes, and also to ensure that bookmarks or URLs passed from one user to another do the expected thing. But I'm having a lot of trouble getting this to work. I would prefer not to have to modify the subs in the existing framework, so I've been trying variations on the following: sub customer : Regex('^(\w+)/(admin)$') { my ($self, $c, @args) = @_; #validation of captured arg snipped.. my $path = join('/', 'admin', @args); $c->request->path($path); $c->dispatcher->prepare_action($c); $c->forward($c->action, $c->req->args); } But it just will not behave. I've used regex matching actions many times, but putting one in the very first 'barrel' of a URI seems unusually traumatic. Any suggestions gratefully received.

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  • persist values/variables from page to page

    - by Todd
    Hello, I'm wondering if there's another solution to my problem, that's considered more the Sharepoint way. FIrstly, my site is an Internet site, not Intranet. The problem is, all I'm trying to do is save values/variables from page to page in Sharepoint. I know the issue with Session Variables, but this seems to be the only way I can see to accomplish this. I know there are webparts that can store this value, but am I wrong in thinking this won't be persisted from page to page? Basically, I'll be extending the Content Query Web Part to dynamically filter it's results based off of a variable/value. The user chooses their 'area' from a dropdown, and the CQWP in the site will change and query results based off of this value (It will be a provincial structure as it is a Canadian site, so if someone chooses the province 'Ontario', this value is saved in a global variable, and these extended CQWP that are throughout the site, will get this value, and query lists flagged as Ontario). Is Session variables the only solution? Thanks everyone!

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  • design pattern for related inputs

    - by curiousMo
    My question is a design question : let's say i have a data entry web page with 4 drop down lists, each depending on the previous one, and a bunch of text boxes. ddlCountry (DropDownList) ddlState (DropDownList) ddlCity (DropDownList) ddlBoro (DropDownList) txtAddress (TxtBox) txtZipcode(TxtBox) and an object that represents a datarow with a value for each: countrySeqid stateSeqid citySeqid boroSeqid address zipCode naturally the country, state, city and boro values will be values of primary keys of some lookup tables. when the user chooses to edits that record, i would load it from database and load it into the page. the issue that I have is how to streamline loading the DropDownLists. i have some code that would grab the object,look thru its values and move them to their corresponding input controls in one shot. but in this case i will have to load the ddlCountry with possible values, then assign values, then do the same thing for the rest of the ddls. I guess i am looking for an elegant solution. i am using asp.net, but i think it is irrelevant to the question. i am looking more into a design pattern.

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  • Binding Listbox item source to a collection of collections in windows phone 7

    - by Tee
    Hi there, I am trying to bind a Listbox ItemSource to a collection of multiple Lists. i.e. List PersonCollection List Person List Collection Now I need to show items from both of these list. In wpf you could use HierarchicalDataTemplate i believe, but not sure how I can do it in windows phone 7. Tried with Blend and it generates the following data template. <DataTemplate x:Key="PersonDataTemplate"> <Grid> <StackPanel Margin="0,0,1,0" Orientation="Vertical" VerticalAlignment="Top"> <TextBlock Margin="0,0,1,0" TextWrapping="Wrap" Text="{Binding Person[0].Name}" d:LayoutOverrides="Width"/> <TextBlock Margin="0,0,1,0" TextWrapping="Wrap" Text="{Binding Collection[0].Total}" d:LayoutOverrides="Width"/> </StackPanel> </Grid> </DataTemplate> Is there another way I can do this? I have tried to set the DataContext of Textbox in DataTemplate to individual arrays but did not seem to work. Cant find anything similar on the net apart from the confirmation that HierarchicalDataTemplate is not supported in Windows Phone 7. I have other ways to do but none elegant.. Thanks in advance. Regards

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  • Advanced All In One .NET Framework (should i go for a software factory ?)

    - by alfredo dobrekk
    Hi, i m starting a new project that would basically take input from user and save them to database among about 30 screens, and i would like to find a framework that will allow the maximum number of these features out of the box : .net c#. windows form. unit testing continuous integration logging screens with lists, combo boxes, text boxes, add, delete, save, cancel that are easy to update when you add a property to your classes or a field to your database. auto completion on controls to help user find its way use of an orm like nhibernate easy multithreading and display of wait screens for user easy undo redo tabbed child windows search forms ability to grant access to some functionnalities according to user profiles mvp/mvvm or whatever design patterns either some code generation from database to c# classe or generation of database schema from c# classes some kind of database versioning / upgrade to easily update database when i release patches to application once in production automatic control resizing code metrics analysis some code generator i can use against my entities that would generate some rough form i can rearrange after code documentation generator ... At this point i have 3 options : Build from scratch on top of clr :( Find functionnalities among several open source framework and use them as a stack for infrastucture Find a "software factory" I know its lot but i really would like to use existing code to build upon so i can focus on business rules. What open source tools would u use to achieve these ?

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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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  • 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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  • 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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  • Capturing output of find . -print0 into a bash array

    - by Idris
    Using find . -print0 seems to be the only safe way of obtaining a list of files in bash due to the possibility of filenames containing spaces, newlines, quotation marks etc. However, I'm having a hard time actually making find's output useful within bash or with other command line utilities. The only way I have managed to make use of the output is by piping it to perl, and changing perl's IFS to null: find . -print0 | perl -e '$/="\0"; @files=<>; print $#files;' This example prints the number of files found, avoiding the danger of newlines in filenames corrupting the count, as would occur with: find . | wc -l As most command line programs do not support null-delimited input, I figure the best thing would be to capture the output of find . -print0 in a bash array, like I have done in the perl snippet above, and then continue with the task, whatever it may be. How can I do this? This doesn't work: find . -print0 | ( IFS=$'\0' ; array=( $( cat ) ) ; echo ${#array[@]} ) A much more general question might be: How can I do useful things with lists of files in bash?

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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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  • 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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  • 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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  • 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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  • GET and POST on the same page?

    - by Phil
    I am creating a commenting script and I came across a problem. I am having to use $_POST and $_GET on the same page, which I don't think makes sense. I am very new to php and am training myself. I have a page named viewVerses.php - this has a lists of verses. When someone follows the reply link, echo '<br /><a href="reply.php?verseid='.$verseid.'">Reply</a>'; I'm passing the verseid (commenting on bible verses) into the reply.php, so that a query may be made with that verseid. (This is so that the user can still see the verse he/she is commenting on). Now reply.php has the form in it for posting a reply. The form goes to postReply.php This is in postReply.php $title = $_POST['title']; $body = $_POST['body']; $verseid = $_GET[verseid]; Can I get the verseid from the url and the POST the values from the form in the same page? If not, is there a way I can do this better? Remember, I am new at php and probably won't implement a solution that is super hard. I have to get it for my to put it in my site. I hope this is clear

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  • HashMap Memory Leak because of Dynamic Array

    - by Jake M
    I am attempting to create my own HashMap to understand how they work. I am using an array of Linked Lists to store the values(strings) in my hashmap. I am creating the array like this: Node** list; Instead of this: Node* list[nSize]; This is so the array can be any size at runtime. But I think I am getting a memory leak because of how I am doing this. I dont know where the error is but when I run the following simple code the .exe crashes. Why is my application crashing and how can I fix it? Note: I am aware that using a vector would be much better than an array but this is just for learning and I want to challenge myself to create the hashmap using a 'Dynamic' Array. PS: is that the correct term(Dynamic Array) for the kind of array I am using? struct Node { // to implement }; class HashMap { public: HashMap(int dynSize) { *list = new Node[dynSize]; size = dynSize; for (int i=0; i<size; i++) list[i] = NULL; cout << "END\n"; } ~HashMap() { for (int i=0; i<size; i++) delete list[i]; } private: Node** list; // I could use a vector here but I am experimenting with a pointer to an array(pointer), also its more elegant int size; }; int main() { // When I run this application it crashes. Where is my memory leak? HashMap h(5); system("PAUSE"); return 0; }

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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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  • 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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  • 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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  • Scheme Function to reverse elements of list of 2-list

    - by sudhirc
    This is an exercise from EOPL. Procedure (invert lst) takes lst which is a list of 2-lists and returns a list with each 2-list reversed. (define invert (lambda (lst) (cond((null? lst ) '()) ((= 2 (rtn-len (car lst))) ( cons(swap-elem (car lst)) (invert (cdr lst)))) ("List is not a 2-List")))) ;; Auxiliry Procedure swap-elements of 2 element list (define swap-elem (lambda (lst) (cons (car (cdr lst)) (car lst)))) ;; returns lengh of the list by calling (define rtn-len (lambda (lst) (calc-len lst 0))) ;; calculate length of the list (define calc-len (lambda (lst n) (if (null? lst) n (calc-len (cdr lst) (+ n 1))))) This seems to work however looks very verbose. Can this be shortened or written in more elegant way ? How I can halt the processing in any of the individual element is not a 2-list? At the moment execution proceed to next member and replacing current member with "List is not a 2-List" if current member is not a 2-list.

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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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  • xhtml validator

    - by lolalola
    Hi, why w3 validator show error? "Line 5, Column 7: end tag for "head" which is not finished </head> Most likely, you nested tags and closed them in the wrong order. For example <p><em>...</p> is not acceptable, as <em> must be closed before <p>. Acceptable nesting is: <p><em>...</em></p> Another possibility is that you used an element which requires a child element that you did not include. Hence the parent element is "not finished", not complete. For instance, in HTML the <head> element must contain a <title> child element, lists require appropriate list items (<ul> and <ol> require <li>; <dl> requires <dt> and <dd>), and so on. " My code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" > <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> </head> <body> Text... </body> </html>

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  • Trouble swapping values as keys in generic java BST class

    - by user1729869
    I was given a generic binary search tree class with the following declaration: public class BST<K extends Comparable<K>, V> I was asked to write a method that reverses the BST such that the values become the keys and keys become values. When I call the following method (defined in the class given) reverseDict.put(originalDict.get(key), key); I get the following two error messages from Netbeans: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: BST.put And also: no suitable method found for put(V,K) method BST.put(BST<K,V>.Node,K,V) is not applicable (actual and formal argument lists differ in length) method BST.put(K,V) is not applicable (actual argument V cannot be converted to K by method invocation conversion) where V,K are type-variables: V extends Object declared in method <K,V>reverseBST(BST<K,V>) K extends Comparable<K> declared in method <K,V>reverseBST(BST<K,V>) From what the error messages are telling me, since my values do not extend Comparable I am unable to use them as keys. If I am right, how can I get around that without changing the class given (maybe a cast)?

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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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