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• Can anyone give me a sample java socket programming for doing a peer to peer for 3 systems?

  - by Sadesh Kumar N

  I am doing an university project. I need some sample programs on peer to peer programs in java socket programming. Every where people are telling to add a server socket in the client program. I am in a confusion. Can a single program having server socket and client socket will do or i have to create two programs of one initiating a system and another peer program running thrice to solve the problem. or i need to create three programs for three peer systems. I am not clear on the architecture of building peer to peer programs using java sockets. Can some one help me giving a simple program on how to create a peer to peer connection between three systems. I know how to do a socket program for client server model and clear on the concept. But creating a peer to peer architecture sounds complex for me to understand. I also referred this thread. developing peer to peer in java The person commented second says" To make peer2peer app each client opens server socket too. When client A wishes to connect to client B it just connects to its socket. " Need some more sample and an explanation on how peer to peer java socket program works I dont want any external api like jxta to do this task. I need a clear picture on how it works alone with an example.

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• What do I need to do besides code?

  - by user151841

  I'm a single-person operation for my small employer. I'm working on a couple of web applications that have grown to medium-size. We have backups going and everything is in version control with Subversion. I have comments in my code, but documentation outside of code is "spotty at best", and frequently things change. What do I need to do to bring it to the next level, beyond a pile of ( version-controlled, well-commented ) code? What would you say is required to have a robust set of documentation outside of the codebase itself, where the project is at, and where it's going? Ideally I would like some integrated system that would go from brainstorm, to requirements, to tracking bugs and features in svn check-in messages, to documentation. Would trac or redmine do something like this? I would like to show to my boss, "This is the prioritized list of features, this is where we are now, this is how long I spend on this feature, how long I spent on this bug" and I'd like to spend the minimum amount of time managing the projects :) What about ERD and UML diagrams? Is a project incomplete without them?

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• Parallelize or vectorize all-against-all operation on a large number of matrices?

  - by reve_etrange

  I have approximately 5,000 matrices with the same number of rows and varying numbers of columns (20 x ~200). Each of these matrices must be compared against every other in a dynamic programming algorithm. In this question, I asked how to perform the comparison quickly and was given an excellent answer involving a 2D convolution. Serially, iteratively applying that method, like so list = who('data_matrix_prefix*') H = cell(numel(list),numel(list)); for i=1:numel(list) for j=1:numel(list) if i ~= j eval([ 'H{i,j} = compare(' char(list(i)) ',' char(list(j)) ');']); end end end is fast for small subsets of the data (e.g. for 9 matrices, 9*9 - 9 = 72 calls are made in ~1 s). However, operating on all the data requires almost 25 million calls. I have also tried using deal() to make a cell array composed entirely of the next element in data, so I could use cellfun() in a single loop: # who(), load() and struct2cell() calls place k data matrices in a 1D cell array called data. nextData = cell(k,1); for i=1:k [nextData{:}] = deal(data{i}); H{:,i} = cellfun(@compare,data,nextData,'UniformOutput',false); end Unfortunately, this is not really any faster, because all the time is in compare(). Both of these code examples seem ill-suited for parallelization. I'm having trouble figuring out how to make my variables sliced. compare() is totally vectorized; it uses matrix multiplication and conv2() exclusively (I am under the impression that all of these operations, including the cellfun(), should be multithreaded in MATLAB?). Does anyone see a (explicitly) parallelized solution or better vectorization of the problem?

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• Experiences wanted: producing a jar artifact in IntelliJ

  - by skiaddict1

  Developing with IntelliJ 9.0.2 Community Edition, on the Mac. This is a follow-up to this post about including jar files in an artifact, which has not received any replies. I'm hoping that the reason is that somehow, in creating my artifact (or setting my project settings), I unwittingly did something which people don't tend to do, and which is causing my problem, and that by asking people here to share how they create jar artifacts and set up projects, I will discover what it is. To recap: I have a Java project which depends on two library files. I need to package up the entire thing, with the jars inlined (such that on doing jar -tfv <filename> I see ALL the classes listed, including the ones in the two libraries), into a single jar file. I can make an artifact, I can add the library files to the Output Layout pane, but I CANNOT, no matter what I do, I cannot get the "Inline Artifact" item in the context menu to be selectable (i.e. non-grey) when I right-click on one or other library file. The thing is, making a jar which contains library files as well as the project code is NOT an unusual situation in the Java world! So I figure there are lots of IntelliJ folks out there who have done what I need to do. And I would really like to hear from you folks. What project settings do you use? (be specific, please :-) And exactly how do you set up your jar artifacts? (again, as many specific details as possible, please :-) Clearly, I'd be particularly interested to hear from folks with similar setups to mine (above) who are successfully doing what I need to do. Grateful thanks in advance, folks.

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• Creating a sort function for a generic list

  - by Andrey

  I have a method for sorting generic lists by the object fields: public static IQueryable<T> SortTable<T>(IQueryable<T> q, string sortfield, bool ascending) { var p = Expression.Parameter(typeof(T), "p"); if (typeof(T).GetProperty(sortfield).PropertyType == typeof(int?)) { var x = Expression.Lambda<Func<T, int?>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } else if (typeof(T).GetProperty(sortfield).PropertyType == typeof(int)) { var x = Expression.Lambda<Func<T, int>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } else if (typeof(T).GetProperty(sortfield).PropertyType == typeof(DateTime)) { var x = Expression.Lambda<Func<T, DateTime>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } // many more for every type return q; } Is there any way I can collapse those ifs to a single generic statement? The main problem is that for the part Expression.Lambda<Func<T, int>> I am not sure how to write it generically.

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• Using Threads to Handle Sockets

  - by user340468

  I am working on a java program that is essentially a chat room. This is an assignment for class so no code please, I am just having some issues determining the most feasible way to handle what I need to do. I have a server program already setup for a single client using threads to get the data input stream and a thread to handle sending on the data output stream. What I need to do now is create a new thread for each incoming request. My thought is to create a linked list to contain either the client sockets, or possibly the thread. Where I am stumbling is figuring out how to handle sending the messages out to all the clients. If I have a thread for each incoming message how can I then turn around and send that out to each client socket. I'm thinking that if I had a linkedlist of the clientsockets I could then traverse the list and send it out to each one, but then I would have to create a dataoutputstream each time. Could I create a linkedlist of dataoutputstreams? Sorry if it sounds like I'm rambling but I don't want to just start coding this, it could get messy without a good plan. Thanks!

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• Difference between these two functions that find Palindromes....

  - by Moin

  I wrote a function to check whether a word is palindrome or not but "unexpectedly", that function failed quite badly, here it is: bool isPalindrome (const string& s){ string reverse = ""; string original = s; for (string_sz i = 0; i != original.size(); ++i){ reverse += original.back(); original.pop_back(); } if (reverse == original) return true; else return false; } It gives me "string iterator offset out of range error" when you pass in a string with only one character and returns true even if we pass in an empty string (although I know its because of the intialisation of the reverse variable) and also when you pass in an unassigned string for example: string input; isPalindrome(input); Later, I found a better function which works as you would expect: bool found(const string& s) { bool found = true; for (string::const_iterator i = s.begin(), j = s.end() - 1; i < j; ++i, --j) { if (*i != *j) found = false; } return found; } Unlike the first function, this function correctly fails when you give it an unassigned string variable or an empty string and works for single characters and such... So, good people of stackoverflow please point out to me why the first function is so bad... Thank You.

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• How do I do a table join on two fields in my second table?

  - by Cannonade

  I have two tables: Messages - Amongst other things, has a to_id and a from_id field. People - Has a corresponding person_id I am trying to figure out how to do the following in a single linq query: Give me all messages that have been sent to and from person x (idself). I had a couple of cracks at this. Not quite right MsgPeople = (from p in db.people join m in db.messages on p.person_id equals m.from_id where (m.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); This almost works, except I think it misses one case: "people who have never received a message, just sent one to me" How this works in my head So what I really need is something like: join m in db.messages on (p.people_id equals m.from_id or p.people_id equals m.to_id) Gets me a subset of the people I am after It seems you can't do that. I have tried a few other options, like doing two joins: MsgPeople = (from p in db.people join m in AllMessages on p.person_id equals m.from_id join m2 in AllMessages on p.person_id equals m2.to_id where (m2.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); but this gives me a subset of the results I need, I guess something to do with the order the joins are resolved. My understanding of LINQ (and perhaps even database theory) is embarrassingly superficial and I look forward to having some light shed on my problem.

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• cURL/PHP Request Executes 50% of the Time

  - by makavelli

  After searching all over, I can't understand why cURL requests issued to a remote SSL-enabled host are successful only 50% or so of the time in my case. Here's the situation: I have a sequence of cURL requests, all of them issued to a HTTPS remote host, within a single PHP script that I run using the PHP CLI. Occasionally when I run the script the requests execute successfully, but for some reason most of the times I run it I get the following error from cURL: * About to connect() to www.virginia.edu port 443 (#0) * Trying 128.143.22.36... * connected * Connected to www.virginia.edu (128.143.22.36) port 443 (#0) * successfully set certificate verify locations: * CAfile: none CApath: /etc/ssl/certs * error:140943FC:SSL routines:SSL3_READ_BYTES:sslv3 alert bad record mac * Closing connection #0 If I try again a few times I get the same result, but then after a few tries the requests will go through successfully. Running the script after that again results in an error, and the pattern continues. Researching the error 'alert bad record mac' didn't give me anything helpful, and I hesitate to blame it on an SSL issue since the script still runs occasionally. I'm on Ubuntu Server 10.04, with php5 and php5-curl installed, as well as the latest version of openssl. In terms of cURL specific options, CURLOPT_SSL_VERIFYPEER is set to false, and both CURLOPT_TIMEOUT and CURLOPT_CONNECTTIMEOUT are set to 4 seconds. Further illustrating this problem is the fact that the same exact situation occurs on my Mac OS X dev machine - the requests only go through ~50% of the time.

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• Triangulation in 3D Space

  - by w3b_wizzard

  Disclaimer: This is for class, however I'm fresh out of ideas and a nudge in the right direction would be much appreciated. Also, this needs to be implemented in raw C, so no fancy libraries can be used. I have to write a search and rescue simulator for submarines, it has to find a probe that is randomly placed in 3D space in a grid from of the MAX_XYZ (100000). The only tools I'm given are a "ping" which will give the magnitude of the distance between a certain sub and the probe. The goal is to optimize the costs of this entire operation so a brute force attempt, like looking at every single coordinate, won't work. Hence I was thinking triangulation. Now, it makes loads of sense to me, place three subs, each one of them uses their ping to get the distance between them and the probe. Since each sub have a known distance relative to one another, it's easy to build the base of a tetrahedron with them, and the results of the ping will point to a certain coordinate, the problem I'm having is how to figure out the elevation, or the height, of the tetrahedron. So what I have as data is the following: Distances between subs (In vector format) Angles between each subs (very easy to compute) Distance between each sub and the probe (3 segments from the base to the peak) Angles inside each of the outer 3 surfaces of the tetrahedron. I tried finding some sort of relationship with the vertices of the tetrahedron and the relative angles in each of them, however all I found had to deal with tetrahedrons built with equilateral triangles, which isn't much help. I have the impression this can be easily solved with trig but either I'm not seeing it or I need more coffee. Any suggestions would be appreciated!

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• how to compare two tables fields name with another value in mysql?

  - by I Like PHP

  I have two tables table_school school_open_time|school_close_time|school_day 8:00 AM | 9:00PM | Monday 10:00 AM | 7:00PM | Wednesday table_college college_open_time|college_close_time|college_day 10:00 AM | 8:00PM | Monday 10:00 AM | 9:00PM | Tuesday 10:00 AM | 5:00PM | Wednesday Now I want to select school_open_time school_close time, college_open_time and college_close_time according to today (means college_day=school_day=today), and also if there is no row for a specific day in any of one table then it display blank field ( LEFT JOIN , I think I can use). Please suggest me best and optimized query for this. UPDATE: if there is no open time and close time for school then college_open_time and college_close_time has to be returned( not to be filled in database,just return) as school_open_time and school_close_time. and there always must be college_open_time and college_close_time for a given day MORE UPDATE: i m using below query SELECT college_open_time,college_close_time ,school_open_time, school_close_time FROM tbl_college LEFT JOIN tbl_school ON school_owner_id=college_owner_id WHERE college_owner_id='".$_session['user_id']."' AND college_day='".date('l',time())."'"; it return single row (left hand having some value and right hand having blank value) when there is no row of a given day in table_school, BUT display seven rows with same value on left hand side(college_open_time, college_close_time) and 6 blank row on right hand side (school_open_time and school_close_time) i need only one row when both table have a row of a given day but using above query take only first row of corresponding table_school where school_owner_id is 50(let), it not see the condition that school_day name should be given day

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• ASP.NET Custom Control - Template Allowing Literal Content

  - by Bob Fincheimer

  I want my User Control to be able to have Literal Content inside of it. For Example: <fc:Text runat="server">Please enter your login information:</fc:Text> Currently the code for my user control is: <ParseChildren(True, "Content")> _ Partial Public Class ctrFormText Inherits FormControl Private _content As ArrayList <PersistenceMode(PersistenceMode.InnerDefaultProperty), _ DesignerSerializationVisibility(DesignerSerializationVisibility.Content), _ TemplateInstance(TemplateInstance.Single)> _ Public Property Content() As ArrayList Get If _content Is Nothing Then Return New ArrayList End If Return _content End Get Set(ByVal value As ArrayList) _content = value End Set End Property Protected Overrides Sub CreateChildControls() If _content IsNot Nothing Then ctrChildren.Controls.Clear() For Each i As Control In _content ctrChildren.Controls.Add(i) Next End If MyBase.CreateChildControls() End Sub End Class And when I put text inside this control (like above) i get this error: Parser Error Message: Literal content ('Please enter your login information to access CKMS:') is not allowed within a 'System.Collections.ArrayList'. This control could have other content than just the text, so making the Content property an attribute will not solve my problem. I found in some places that I need to implement a ControlBuilder Class, along with another class that implements IParserAccessor. Anyway I just want my default "Content" property to have all types of controls allowed in it, both literal and actual controls.

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• How can I simplify this user interface?

  - by Bears will eat you

  I'm writing an internal-tools webapp; one of the central pages in this tool has a whole bunch of related commands the user can execute by clicking one of a number of buttons on the page, like this: Ideally, all of the buttons would fit on one line. Ordinarily I'd do this by changing each widget from a button with a (sometimes long) text label to a simple, compact icon - e.g. could be replaced by a familiar disk icon: Unfortunately, I don't think I can do this for every button on this particular page. Some of the command buttons just don't have good visual analogs - "VDS List". Or, if I needed to add another button in the future for some other kind of list, I'd need two icons that both communicate "list-ness" and which list. So, I'm still considering this option, but I don't love it. So it's come time for me to add yet another button to this section (don't you love internal tools?). There's not enough room on that single line to fit the new button. Aside from the icon solution I already mentioned, what would be a good* way to simplify/declutter/reduce or otherwise improve this UI? *As per Jakob Nielsen's article, I'd like to think that a dropdown menu is not the solution.

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• MS SQL - High performance data inserting with stored procedures

  - by Marks

  Hi. Im searching for a very high performant possibility to insert data into a MS SQL database. The data is a (relatively big) construct of objects with relations. For security reasons i want to use stored procedures instead of direct table access. Lets say i have a structure like this: Document MetaData User Device Content ContentItem[0] SubItem[0] SubItem[1] SubItem[2] ContentItem[1] ... ContentItem[2] ... Right now I think of creating one big query, doing somehting like this (Just pseudo-code): EXEC @DeviceID = CreateDevice ...; EXEC @UserID = CreateUser ...; EXEC @DocID = CreateDocument @DeviceID, @UserID, ...; EXEC @ItemID = CreateItem @DocID, ... EXEC CreateSubItem @ItemID, ... EXEC CreateSubItem @ItemID, ... EXEC CreateSubItem @ItemID, ... ... But is this the best solution for performance? If not, what would be better? Split it into more querys? Give all Data to one big stored procedure to reduce size of query? Any other performance clue? I also thought of giving multiple items to one stored procedure, but i dont think its possible to give a non static amount of items to a stored procedure. Since 'INSERT INTO A VALUES (B,C),(C,D),(E,F) is more performant than 3 single inserts i thought i could get some performance here. Thanks for any hints, Marks

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• How do I automatically update hundreds of images in an HTML page using jquery?

  - by Chris

  I have an HTML page where I want to refresh a lot of images every 30 seconds after the HTML page has been downloaded. I understand how to do this with Jquery and a single image, but I want to use about 200 custom urls to determine the current image to display for over 200 images. I need to find an efficient way to have jquery call the custom url associated with each image to download the url for the needed image as it changes, and then update the image in the page when it changes. Current hyperlink example to demonstrate the custom urls. <A href="/urlThatReturnsCurrentImageURL/1234/4567">link to url for image</A> Each custom url will return an image tag like this (or any other text that makes this simpler for jquery) <img src="/static/someImage.jpg"> What is the simplest way to have jquery call the custom url for each image to download the image url, image html, or some other text that jquery can use to download the right image every 30 seconds? Please keep in mind that I will have about 200 of these on a page.

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• In maven2, how do I assemble bits and pieces of different modules to create final distributions?

  - by Carcassi

  I have four maven project: client api jar web service war ui jar web interface war The service war will need to be packaged to include the client api jar, together with javadocs (so that each version is distributed with a matching client and documentation). The web interface war will need the ui jar and all the dependencies (webstart/applet deployment). So I need a 5th project that does all the packaging. How to do this with ant or a script is perfectly clear to me, but not in maven. I tried the following: having the javadocs included as part of the war packaging: this requires the execution of the javadocs goal in project 1 before execution of package in project 2. Haven't found a way to bind plugins/goals across different projects. Using the assembly plugin in project2 had the same problem. create a fifth project and use the assembly plugin. Still the same problems as before, with the problem that since I need different pieces from each sub-project I do not understand how this can be done using the assembly. Is this too hard to do in maven, and should I just give up? Or I am looking at it wrong, in which case, how should I be looking at it? Thanks! Upon further reflection, here is a partial answer: Each project should build all its artifacts. This is done by having the plugins configured to run as per the prepare-resources and package phases. So, in my case, I prepare all that needs to be generated (jar, javadocs, xsd documentation, ...) as different artifacts so that a single "package" goal execution creates all. So, it's not "how project 2 forces project 1 to run different goals", but it's "make project 1 create all of its artifact as part as the normal lifecycle). This seems to simplify things.

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• Fast compiler error messages in Eclipse

  - by Chris Conway

  As a new Eclipse user, I am constantly annoyed by how long it takes compiler error messages to display. This is mostly only a problem for long errors that don't fit in the status bar or the "Problems" tab. But I get enough long errors in Java—especially with generics—that this is a nagging issue. (Note: The correct answer to this question is not "get better at using generics." ;-) The ways I have found to display an error are: Press Ctrl+. or execute the command "Next Annotation". The next error is highlighted and its associated message appears in the status bar (if it is short enough). The error is also highlighted in the "Problems" tab, if it is open, but the tab is not automatically brought to the top. Hover the mouse over the error. After a noticeable lag, the error message appears as a "tool tip", along with any associated "Quick Fixes." Hover the mouse over the error icon on the left side of the editing pane. After a noticeable lag, all of the error messages for that line appear as a "tool tip." Clicking on the icon brings up "Quick Fixes." What I would like is for Ctrl+. to automatically and instantly bring up the complete error message (I don't care where). Is this a configurable option? [UPDATE] @asterite's "Ctrl+. F2" is almost it. How do I make "Next Annotation, then Show Tooltip Description" a macro bound to a single keystroke?

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• Preserve name of file using cURL to transfer files

  - by Toby

  I'm transferring files from an existing http request using cURL like so... $postargs = array( 'nonfilefield' =>'nonfilevalue', 'fileentry' => '@'.$_FILES['thefile']['tmp_name'][0] ); $ch = curl_init('http://localhost/curl/rec.php'); curl_setopt($ch,CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)"); curl_setopt($ch,CURLOPT_RETURNTRANSFER, true); curl_setopt($ch,CURLOPT_POST,TRUE); curl_setopt($ch,CURLOPT_POSTFIELDS,$postargs); curl_exec($ch); curl_close($ch); The only way I can get this to work is using the tmp_name, without this it won't send. However, I then lose the name value for when I want to name the file later. Is there some way to do this preserving the $_FILES array as it normally would be without curl? I'm also using an array of file fields in my script, so at the moment I have to convert my multidimensional array into a single dimension for this to work

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• syntax for MySQL INSERT with an array of columns

  - by Mike_Laird

  I'm new to PHP and MySQL query construction. I have a processor for a large form. A few fields are required, most fields are user optional. In my case, the HTML ids and the MySQL column names are identical. I've found tutorials about using arrays to convert $_POST into the fields and values for INSERT INTO, but I can't get them working - after many hours. I've stepped back to make a very simple INSERT using arrays and variables, but I'm still stumped. The following line works and INSERTs 5 items into a database with over 100 columns. The first 4 items are strings, the 5th item, monthlyRental is an integer. $query = "INSERT INTO `$table` (country, stateProvince, city3, city3Geocode, monthlyRental) VALUES ( '$country', '$stateProvince', '$city3', '$city3Geocode', '$monthlyRental')"; When I make an array for the fields and use it, as follows: $colsx = array('country,', 'stateProvince,', 'city3,', 'city3Geocode,', 'monthlyRental'); $query = "INSERT INTO `$table` ('$colsx') VALUES ( '$country', '$stateProvince', '$city3', '$city3Geocode', '$monthlyRental')"; I get a MySQL error - check the manual that corresponds to your MySQL server version for the right syntax to use near ''Array') VALUES ( 'US', 'New York', 'Fairport, Monroe County, New York', '(43.09)' at line 1. I get this error whether the array items have commas inside the single quotes or not. I've done a lot of reading and tried many combinations and I can't get it. I want to see the proper syntax on a small scale before I go back to foreach expressions to process $_POST and both the fields and values are arrays. And yes, I know I should use mysql_real_escape_string, but that is an easy later step in the foreach. Lastly, some clues about the syntax for an array of values would be helpful, particularly if it is different from the fields array. I know I need to add a null as the first array item to trigger the MySQL autoincrement id. What else? I'm pretty new, so please be specific.

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• How to know the type of an object in a list?

  - by nacho4d

  Hi, I want to know the type of object (or type) I have in my list so I wrote this: void **list; //list of references list = new void * [2]; Foo foo = Foo(); const char *not_table [] = {"tf", "ft", 0 }; list[0] = &foo; list[1] = not_table; if (dynamic_cast<LogicProcessor*>(list[0])) { //ERROR here ;( printf("Foo was found\n"); } if (dynamic_cast<char*> (list[0])) { //ERROR here ;( printf("char was found\n"); } but I get : error: cannot dynamic_cast '* list' (of type 'void*') to type 'class Foo*' (source is not a pointer to class) error: cannot dynamic_cast '* list' (of type 'void*') to type 'char*' (target is not pointer or reference to class) Why is this? what I am doing wrong here? Is dynamic_cast what I should use here? Thanks in advance EDIT: I know above code is much like plain C and surely sucks from the C++ point of view but is just I have the following situation and I was trying something before really implementing it: I have two arrays of length n but both arrays will never have an object at the same index. Hence, or I have array1[i]!=NULL or array2[i]!=NULL. This is obviously a waste of memory so I thought everything would be solved if I could have both kind of objects in a single array of length n. I am looking something like Cocoa's (Objective-C) NSArray where you don't care about the type of the object to be put in. Not knowing the type of the object is not a problem since you can use other method to get the class of a certain later. Is there something like it in c++ (preferably not third party C++ libraries) ? Thanks in advance ;)

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• How do I call C++/CLI (.NET) DLLs from standard, unmanaged non-.NET applications?

  - by tronjohnson

  In the unmanaged world, I was able to write a __declspec(dllexport) or, alternatively, use a .DEF file to expose a function to be able to call a DLL. (Because of name mangling in C++ for the __stdcall, I put aliases into the .DEF file so certain applications could re-use certain exported DLL functions.) Now, I am interested in being able to expose a single entry-point function from a .NET assembly, in unmanaged-fashion, but have it enter into .NET-style functions within the DLL. Is this possible, in a simple and straight-forward fashion? What I have is a third-party program that I have extended through DLLs (plugins) that implement some complex mathematics. However, the third-party program has no means for me to visualize the calculations. I want to somehow take these pre-written math functions, compile them into a separate DLL (but using C++/CLI in .NET), but then add hooks to the functions so I can render what's going on under the hood in a .NET user control. I'm not sure how to blend the .NET stuff with the unmanaged stuff, or what to Google to accomplish this task. Specific suggestions with regard to the managed/unmanaged bridge, or alternative methods to accomplish the rendering in the manner I have described would be helpful. Thank you.

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• Patterns and Libraries for working with raw UI values.

  - by ProfK

  By raw values, I mean the application level values provided by UI controls, such as the Text property on a TextBox. Too often I find myself writing code to check and parse such values before they get used as a business level value, e.g. PaymentTermsNumDays. I've mitigated a lot of the spade work with rough and ready extension methods like String.ToNullableInt, but we all know that just isn't right. We can't put the whole world on String's shoulders. Do I look at tasking my UI to provide business values, using a ruleset pushed out from the server app, or open my business objects up a bit to do the required sanitising etc. as they required? Neither of these approaches sits quite right with me; the first seems closer to ideal, but quite a bit of work, while the latter doesn't show much respect to the business objects' single responsibility. The responsibilities of the UI are a closer match. Between these extremes, I could also just implement another DTO layer, an IoC container with sanitising and parsing services, derive enhanced UI controls, or stick to copy and paste inline drudgery.

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• What am I doing wrong with my ItemsControl & databinding?

  - by Joel

  I'm reworking my simple hex editor to practice using what I've recently learned about data binding in WPF. I'm not sure what I'm doing wrong here. As I understand it, for each byte in the collection "backend" (inherits from ObservableCollection), my ItemsControl should apply the DataTemplate under resources. This template is just a textbox with a binding to a value converter. So I'm expecting to see a row of textboxes, each containing a string representation of one byte. When I use this XAML, all I get is a single line of uneditable text, which as far as I can tell doesn't use a textbox. What am I doing wrong? I've pasted my XAML in below, with the irrelevant parts (Menu declaration, schema, etc) removed. <Window ...> <Window.Resources> <local:Backend x:Key="backend" /> <local:ByteConverter x:Key="byteConverter" /> <DataTemplate DataType="byte"> <TextBox Text="{Binding Converter={StaticResource byteConverter}}" /> </DataTemplate> </Window.Resources> <StackPanel> <ItemsControl ItemsSource="{Binding Source={StaticResource backend}}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <WrapPanel /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </StackPanel> </Window>

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• hash fragments and collisions cont.

  - by Mark

  For this application I've mine I feel like I can get away with a 40 bit hash key, which seems awfully low, but see if you can confirm my reasoning (I want a small key because I want a small filename and the key will be converted to a filename): (Note: only accidental collisions a concern - no security issues.) A key point here is that the population in question is divided into groups, and a collision is only relevant if it occurs within the same group. A "group" is a directory on a user's system (the contents of files are hashed and a collision is only relevant if it occurs for files within the same directory). So with speculating roughly 100,000 potential users, say 2^17, that corresponds to 2^18 "groups" assuming 2 directories per user on average. So with a 40 bit key I can expect 2^(20+9) files created (among all users) before a collision occurs for some user somewhere. (Or IOW 2^((40+18)/2), due to the "birthday effect".) That's an average 4096 unique files created per user, for 2^17 users, before a single collision occurs for some user somewhere. And then that long again before another collision occurs somewhere (right?)

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• Good C++ array class for dealing with large arrays of data in a fast and memory efficient way?

  - by Shane MacLaughlin

  Following on from a previous question relating to heap usage restrictions, I'm looking for a good standard C++ class for dealing with big arrays of data in a way that is both memory efficient and speed efficient. I had been allocating the array using a single malloc/HealAlloc but after multiple trys using various calls, keep falling foul of heap fragmentation. So the conclusion I've come to, other than porting to 64 bit, is to use a mechanism that allows me to have a large array spanning multiple smaller memory fragments. I don't want an alloc per element as that is very memory inefficient, so the plan is to write a class that overrides the [] operator and select an appropriate element based on the index. Is there already a decent class out there to do this, or am I better off rolling my own? From my understanding, and some googling, a 32 bit Windows process should theoretically be able address up to 2GB. Now assuming I've 2GB installed, and various other processes and services are hogging about 400MB, how much usable memory do you think my program can reasonably expect to get from the heap? I'm currently using various flavours of Visual C++.

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