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• printing sequence number of a sniffed packet

  - by scatman

  i am using pcap to create a packet sniffer. i have this tcp structure: typedef struct TSP_header{ unsigned short int sport; unsigned short int dport; unsigned int seqnum; unsigned int acknum; unsigned char reserved:4, offset:4; unsigned int tcp_res1:4, //little-endian tcph_hlen:4, //length of tcp header in 32-bit words tcph_fin:1, //Finish flag "fin" tcph_syn:1, //Synchronize sequence numbers to start a connection tcph_rst:1, //Reset flag tcph_psh:1, //Push, sends data to the application tcph_ack:1, //acknowledge tcph_urg:1, //urgent pointer tcph_res2:2; unsigned short int tcph_win; unsigned short int tcph_chksum; unsigned short int tcph_urgptr; }TSP_header; how can i print the sequence number? shou i use htons(sequence_number)?? coz it isn't working this way!!

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• TinyMCE: Double forecolor and backcolor buttons?

  - by petsson

  I'm having a problem using TinyMCE. In IE8, the forecolor and backcolor, for some random reason, is displayed twice. See picture below. Source code (I add the forecolor and backcolor in theme_advanced_buttons2): tinyMCE.init({ mode : "exact", elements : "<%= editArea.ClientID %>", custom_shortcuts : false, language : "en", relative_urls : false, convert_urls : false, forced_root_block : false, force_p_newlines : true, force_br_newlines : false, fix_nesting : true, plugins : "pagebreak,table", pagebreak_separator : '<div style="page-break-after:always;"></div>', theme : "advanced", skin : "o2k7", skin_variant : "blue", width : "540", height : "470", theme_advanced_toolbar_location : "top", theme_advanced_statusbar_location : "none", theme_advanced_font_sizes : "1,2,3,4,5,6,7", font_size_style_values : "0.6em,0.8em,1em,1.2em,1.5em,2em,3em", theme_advanced_buttons1 : "newdocument,|,copy,cut,paste,|,hr,pagebreak,|,undo,redo,|,code|,image,code", theme_advanced_buttons2 : "fontselect,fontsizeselect,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,forecolor,backcolor", // <-- This gives me double forecolor and backcolor theme_advanced_buttons3 : "table,|,row_props,cell_props,|,col_before,col_after,row_before,row_after,|,split_cells,merge_cells,|,delete_col,delete_row," });

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• Prim's MST algorithm implementation with Java

  - by user1290164

  I'm trying to write a program that'll find the MST of a given undirected weighted graph with Kruskal's and Prim's algorithms. I've successfully implemented Kruskal's algorithm in the program, but I'm having trouble with Prim's. To be more precise, I can't figure out how to actually build the Prim function so that it'll iterate through all the vertices in the graph. I'm getting some IndexOutOfBoundsException errors during program execution. I'm not sure how much information is needed for others to get the idea of what I have done so far, but hopefully there won't be too much useless information. This is what I have so far: I have a Graph, Edge and a Vertex class. Vertex class mostly just an information storage that contains the name (number) of the vertex. Edge class can create a new Edge that has gets parameters (Vertex start, Vertex end, int edgeWeight). The class has methods to return the usual info like start vertex, end vertex and the weight. Graph class reads data from a text file and adds new Edges to an ArrayList. The text file also tells us how many vertecis the graph has, and that gets stored too. In the Graph class, I have a Prim() -method that's supposed to calculate the MST: public ArrayList<Edge> Prim(Graph G) { ArrayList<Edge> edges = G.graph; // Copies the ArrayList with all edges in it. ArrayList<Edge> MST = new ArrayList<Edge>(); Random rnd = new Random(); Vertex startingVertex = edges.get(rnd.nextInt(G.returnVertexCount())).returnStartingVertex(); // This is just to randomize the starting vertex. // This is supposed to be the main loop to find the MST, but this is probably horribly wrong.. while (MST.size() < returnVertexCount()) { Edge e = findClosestNeighbour(startingVertex); MST.add(e); visited.add(e.returnStartingVertex()); visited.add(e.returnEndingVertex()); edges.remove(e); } return MST; } The method findClosesNeighbour() looks like this: public Edge findClosestNeighbour(Vertex v) { ArrayList<Edge> neighbours = new ArrayList<Edge>(); ArrayList<Edge> edges = graph; for (int i = 0; i < edges.size() -1; ++i) { if (edges.get(i).endPoint() == s.returnVertexID() && !visited(edges.get(i).returnEndingVertex())) { neighbours.add(edges.get(i)); } } return neighbours.get(0); // This is the minimum weight edge in the list. } ArrayList<Vertex> visited and ArrayList<Edges> graph get constructed when creating a new graph. Visited() -method is simply a boolean check to see if ArrayList visited contains the Vertex we're thinking about moving to. I tested the findClosestNeighbour() independantly and it seemed to be working but if someone finds something wrong with it then that feedback is welcome also. Mainly though as I mentioned my problem is with actually building the main loop in the Prim() -method, and if there's any additional info needed I'm happy to provide it. Thank you. Edit: To clarify what my train of thought with the Prim() method is. What I want to do is first randomize the starting point in the graph. After that, I will find the closest neighbor to that starting point. Then we'll add the edge connecting those two points to the MST, and also add the vertices to the visited list for checking later, so that we won't form any loops in the graph. Here's the error that gets thrown: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.rangeCheck(Unknown Source) at java.util.ArrayList.get(Unknown Source) at Graph.findClosestNeighbour(graph.java:203) at Graph.Prim(graph.java:179) at MST.main(MST.java:49) Line 203: return neighbour.get(0); in findClosestNeighbour() Line 179: Edge e = findClosestNeighbour(startingVertex); in Prim()

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• Regular Expressions, Checking for a range of occurrences

  - by gmcalab

  I have a phone number I want to match against a regular expression. The format of the phone number must match this: (123) 123-4567 x12345 The extension is optional. Also the extension must contain 1-5 numbers. Below is a regular expression I wrote that works. ^\(\d{3}\) \d{3}-\d{4}( x\d\d?\d?\d?\d?)?$ I was wondering if there is a better way to check for the extension instead of x\d\d?\d?\d?\d? Can I say 1-5 occurrences of \d instead of the above some how ?

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• Problems with Linked List in C

  - by seePhor

  Hey everyone, I am new to C and I am working on an XOR linked list for a project. I have most of the code done, but I can't seem to get the delete function of the list to work properly. It seems able to delete some numbers, but not any number you pass into the function. Could anyone experienced with C take a look and possibly point out where I went wrong? I have been working on this for a while now and have not had much luck and I have started over 3 times :( Any help is much appreciated. Thank you. You can see my first attempt of code here. I can only post one link, so if you would like to see my second attempt, just tell me so and I can email it to you or something. Thank you for your time.

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• How do I randomly fill an array in Java?

  - by Kat

  I'm writing a program that creates a 2D array from a integer n. I then have to fill the array with values from 1 to the n*n array size and check to see if it is a magic square. The way I am doing it now fills the array in order from 1 to n*n array size. How can I make that random? My code: System.out.print("Enter an whole number: "); int n = scan.nextInt(); int [][] magic = new int [n][n]; for (int row = 0; row < magic.length; row++) { for(int col = 0; col < magic[row].length; col++) magic[row][col] = ((row * n) + 1) + col; }

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• How is schoolbook long division an O(n^2) algorithm?

  - by eSKay

  Premise: This Wikipedia page suggests that the computational complexity of Schoolbook long division is O(n^2). Deduction: Instead of taking "Two n-digit numbers", if I take one n-digit number and one m-digit number, then the complexity would be O(n*m). Contradiction: Suppose you divide 100000000 (n digits) by 1000 (m digits), you get 100000, which takes six steps to arrive at. Now, if you divide 100000000 (n digits) by 10000 (m digits), you get 10000 . Now this takes only five steps. Conclusion: So, it seems that the order of computation should be something like O(n/m). Question: Who is wrong, me or Wikipedia, and where?

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• Visual Artifacts in Visual Studio 2010

  - by Simon Chadwick

  I'm using VS 2010 on Windows Server 2003, running on a Dell Inspiron 9400 laptop. VS 2010 runs fine, except for persistent and random screen re-drawing issues. Samples of these are here. These artifacts occur as the mouse moves over items that highlight on a mouse-over event, while scrolling, and when switching tabs. VS 2008 has non of these issues, so I assume that it is related to VS 2010's use of WPF. Could it be that my video card or driver is not up to the task of rendering WPF? Some other WPF applications (not Silverlight) also have some of these screen repainting problems. I have tried a variety of settings in System Properties--Advanced--Performance Options--Visual Effects, and in the related "Advanced" tab, Processor Scheduling is adjusted for best performance of programs. Many thanks for any suggestions!

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• How do you diagnose a 500 error on Heroku when there is no error message in the logs?

  - by lala

  I have a Rails app on Heroku that is serving 500 errors at random intervals. Web pages will display "Internal server error" in plain text, instead of the usual "We're sorry. Something went wrong." page. When I refresh the page, it works fine. The logs don't show me an error message, just » 14:20:34.107 2013-10-11 12:20:33.763690+00:00 heroku router - - at=info method=HEAD path=/ host=www.mydomain.com fwd="184.73.237.85/ec2-184-73-237-85.compute-1.amazonaws.com" dyno=web.1 connect=1ms service=63ms status=200 bytes=0 » 14:21:03.957 2013-10-11 12:21:03.561867+00:00 heroku router - - at=info method=GET path=/ host=www.mydomain.com fwd="50.112.95.211/ec2-50-112-95-211.us-west-2.compute.amazonaws.com" dyno=web.1 connect=0ms service=1ms status=500 bytes=21 Support has told me to look at request queuing in New Relic, but New Relic only shows a big red mark saying the server is down (even though the site works fine when refreshed). With no error messages, I'm at a loss for how to diagnose this issue.

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• HTTP Content-type header for cached files

  - by Brian

  Hello, Using Apache with mod_rewrite, when I load a .css or .js file and view the HTTP headers, the Content-type is only set correctly the first time I load it - subsequent refreshes are missing Content-type altogether and it's creating some problems for me. I can get around this by appending a random query string value to the end of each filename, eg. http://www.site.com/script.js?12345 However, I don't want to have to do that, since caching is good and all I want is for the Content-type to be present. I've tried using a RewriteRule to force the type but still didn't solve the problem. Any ideas? Thanks, Brian

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• OpenID and Authlogic - login and password?

  - by skrat

  How can I get rid of validation messages telling me that: Login is too short (minimum is 3 characters) Login should use only letters, numbers, spaces, and .-_@ please. Password is too short (minimum is 4 characters) Password confirmation is too short (minimum is 4 characters) this happens even before map_openid_registration is called, thus not giving me any chance to fill login with something from returned registration Hash. I would like to have OpenID auto-registration (on login) without requiring user to supply login/password. I also won't make this fields "not required" or "not validated", since I still need them with old school login/password registration. Thank you

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• searching for a programming platform with hot code swap

  - by Andreas

  I'm currently brainstorming over the idea how to upgrade a program while it is running. (Not while debugging, a "production" system.) But one thing that is required for it, is to actually submit the changed source code or compiled byte code into the running process. Pseudo Code var method = typeof(MyClass).GetMethod("Method1"); var content = //get it from a database (bytecode or source code) SELECT content FROM methods WHERE id=? AND version=? method.SetContent(content); At first, I want to achieve the system to work without the complexity of object-orientation. That leads to the following requirements: change source code or byte code of function drop functions add new functions change the signature of a function With .NET (and others) I could inject a class via an IoC and could thus change the source code. But the loading would be cumbersome, because everything has to be in an Assembly or created via Emit. Maybe with Java this would be easier? The whole ClassLoader is replacable, I think. With JavaScript I could achieve many of the goals. Simply eval a new function (MyMethod_V25) and assign it to MyClass.prototype.MyMethod. I think one can also drop functions somehow with "del" Which general-purpose platform can handle such things?

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• Intersection of line with cube and knowing the point of intersection.

  - by Raj

  Hello everyone, description 1.lines are originating from origin(0,0,0). 2.lines are at some random angle to the Normal of Top face of teh cube. 3.if the lines are intersecting cube , calculate the intersection point. 4.mainly i wan to know how much distance ,line traveled inside the cube. I dont know exactly which approach should i take , i will be pleased and thankful if someone could guied me to the right direction, to use OpenGL, DirectX or some other library, for C# . some example or sample will be appriciated.

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• Confusion Matrix with number of classified/misclassified instances on it (Python/Matplotlib)

  - by Pinkie

  I am plotting a confusion matrix with matplotlib with the following code: from numpy import * import matplotlib.pyplot as plt from pylab import * conf_arr = [[33,2,0,0,0,0,0,0,0,1,3], [3,31,0,0,0,0,0,0,0,0,0], [0,4,41,0,0,0,0,0,0,0,1], [0,1,0,30,0,6,0,0,0,0,1], [0,0,0,0,38,10,0,0,0,0,0], [0,0,0,3,1,39,0,0,0,0,4], [0,2,2,0,4,1,31,0,0,0,2], [0,1,0,0,0,0,0,36,0,2,0], [0,0,0,0,0,0,1,5,37,5,1], [3,0,0,0,0,0,0,0,0,39,0], [0,0,0,0,0,0,0,0,0,0,38] ] norm_conf = [] for i in conf_arr: a = 0 tmp_arr = [] a = sum(i,0) for j in i: tmp_arr.append(float(j)/float(a)) norm_conf.append(tmp_arr) plt.clf() fig = plt.figure() ax = fig.add_subplot(111) res = ax.imshow(array(norm_conf), cmap=cm.jet, interpolation='nearest') cb = fig.colorbar(res) savefig("confmat.png", format="png") But I want to the confusion matrix to show the numbers on it like this graphic (the right one): http://i48.tinypic.com/2e30kup.jpg How can I plot the conf_arr on the graphic?

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• Java: confirm method Binary division and find remainder is correct?

  - by cadwag

  I am parsing binary files and have to implement a CRC algorithm to ensure the file is not corrupted. Problem is that I can't seem to get the binary math working when using larger numbers. The example I'm trying to get working: BigInteger G = new BigInteger("11001", 2); BigInteger M = new BigInteger("1110010000", 2); BigInteger R = M.remainder(G); I am expecting: R = "0101" But I am getting: R = "1100" I am assuming the remainder of 0101 is correct since it is given to me in this book I am using as a reference for the CRC algorithm (it's not based in Java), but I can't seem to get it working. I can get small binary calculations to work that I have solved by hand, but not the larger ones. I'll admit that I haven't worked the larger ones by hand yet, that is my next step, but I wanted to see if someone could point out a glaring flaw I have in my code. Can anyone confirm or deny that my methodology is correct? Thanks

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• Using 'load' in octave

  - by lollygagger

  Is there a way to tell the load function to only load until a certain line? I want to read in a data file and assign the numbers to an array, however, I want it to stop after it has created a 200 X 200. Could I also do this with a do-while loop and fgetl? When I try to use fgetl(fid, len) and give it 'len', it does not obey :-/ How can I tell octave to ignore the comment lines in an input file? They are '#' characters, so I figured octave would just automatically ignore them, but not so... Thanks.

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• SQL Server Index cost

  - by yellowstar

  I have read that one of the tradeoffs for adding table indexes in SQL Server is the increased cost of insert/update/delete queries to benefit the performance of select queries. I can conceptually understand what happens in the case of an insert because SQL Server has to write entries into each index matching the new rows, but update and delete are a little more murky to me because I can't quite wrap my head around what the database engine has to do. Let's take DELETE as an example and assume I have the following schema (pardon the pseudo-SQL) TABLE Foo col1 int ,col2 int ,col3 int ,col4 int PRIMARY KEY (col1,col2) INDEX IX_1 col3 INCLUDE col4 Now, if I issue the statement DELETE FROM Foo WHERE col1=12 AND col2 > 34 I understand what the engine must do to update the table (or clustered index if you prefer). The index is set up to make it easy to find the range of rows to be removed and do so. However, at this point it also needs to update IX_1 and the query that I gave it gives no obvious efficient way for the database engine to find the rows to update. Is it forced to do a full index scan at this point? Does the engine read the rows from the clustered index first and generate a smarter internal delete against the index? It might help me to wrap my head around this if I understood better what is going on under the hood, but I guess my real question is this. I have a database that is spending a significant amount of time in delete and I'm trying to figure out what I can do about it. When I display the execution plan for the deletion, it just shows an entry for "Clustered Index Delete" on table Foo which lists in the details section the other indices that need to be updated but I don't get any indication of the relative cost of these other indices. Are they all equal in this case? Is there some way that I can estimate the impact of removing one or more of these indices without having to actually try it?

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• Dispelling the UIImage imageNamed: FUD

  - by Roger Nolan

  I see a lot of people saying imageNamed is bad but equal numbers of people saying the performance is good - especially when rendering UITableViews. See this SO question for example or this article on iPhoneDeveloperTips.com UIImage's imageNamed method used to leak so it was best avoided but has been fixed in recent releases. I'd like to understand the caching algorithm better in order to make a reasoned decision about where I can trust the system to cache my images and where I need to go the extra mile and do it myself. My current basic understanding is that it's a simple NSMutableDictionary of UIImages referenced by filename. It gets bigger and when memory runs out it gets a lot smaller. For example, does anyone know for sure that the image cache behind imageNamed does not respond to didReceiveMemoryWarning? It seems unlikely that Apple would not do this. If you have any insight into the caching algorithm, please post it here.

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• Reading numeric Excel data as text using xlrd in Python

  - by Brian

  Hi guys, I am trying to read in an Excel file using xlrd, and I am wondering if there is a way to ignore the cell formatting used in Excel file, and just import all data as text? Here is the code I am using for far: import xlrd xls_file = 'xltest.xls' xls_workbook = xlrd.open_workbook(xls_file) xls_sheet = xls_workbook.sheet_by_index(0) raw_data = [['']*xls_sheet.ncols for _ in range(xls_sheet.nrows)] raw_str = '' feild_delim = ',' text_delim = '"' for rnum in range(xls_sheet.nrows): for cnum in range(xls_sheet.ncols): raw_data[rnum][cnum] = str(xls_sheet.cell(rnum,cnum).value) for rnum in range(len(raw_data)): for cnum in range(len(raw_data[rnum])): if (cnum == len(raw_data[rnum]) - 1): feild_delim = '\n' else: feild_delim = ',' raw_str += text_delim + raw_data[rnum][cnum] + text_delim + feild_delim final_csv = open('FINAL.csv', 'w') final_csv.write(raw_str) final_csv.close() This code is functional, but there are certain fields, such as a zip code, that are imported as numbers, so they have the decimal zero suffix. For example, is there is a zip code of '79854' in the Excel file, it will be imported as '79854.0'. I have tried finding a solution in this xlrd spec, but was unsuccessful.

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• How do I compute the approximate entropy of a bit string?

  - by dreeves

  Is there a standard way to do this? Googling -- "approximate entropy" bits -- uncovers multiple academic papers but I'd like to just find a chunk of pseudocode defining the approximate entropy for a given bit string of arbitrary length. (In case this is easier said than done and it depends on the application, my application involves 16,320 bits of encrypted data (cyphertext). But encrypted as a puzzle and not meant to be impossible to crack. I thought I'd first check the entropy but couldn't easily find a good definition of such. So it seemed like a question that ought to be on StackOverflow! Ideas for where to begin with de-cyphering 16k random-seeming bits are also welcome...) See also this related question: http://stackoverflow.com/questions/510412/what-is-the-computer-science-definition-of-entropy

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• SQLServer 2008 Pivot

  - by Mitch

  I need to show some information in a graph, the data is held in a SQL Server 2008 table. The graph is expecting 2 columns, one for QuestionNumber and the other for Score. The table containing the data has column names that correspond to the question numbers ie A1, A2, A3, A4, B1, B2, B3, B4, C1, C2. Each question is given a score of 1 to 5. I need to show a graph where the X axis shows A1, A2, A3 etc and the Y axis shows the score. I'm thinking I somehow need to rotate the data to achive this, but I'm not sure how. Maybe a different technique can acheive this rather that a Rotate, so I'm open to any ideas.

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• How to have localized style when writing cell with xlwt

  - by lfagundes

  I'm writing an Excel spreadsheet with Python's xlwt and I need numbers to be formatted using "." as thousands separator, as it is in brazilian portuguese language. I have tried: style.num_format_str = r'#,##0' And it sets the thousands separator as ','. If I try setting num_format_str to '#.##0', I'll get number formatted as 1234.000 instead of 1.234. And if I open document in OpenOffice and format cells, I can set the language of the cell to "Portuguese (Brazil)" and then OpenOffice will show the format code as being "#.##0", but I don't find a way to set the cell's language to brazilian portuguese. Any ideas?

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• Unique identifiers for users

  - by Christopher McCann

  If I have a table of a hundred users normally I would just set up an auto-increment userID column as the primary key. But if suddenly we have a million users or 5 million users then that becomes really difficult because I would want to start becoming more distributed in which case an auto-increment primary key would be useless as each node would be creating the same primary keys. Is the solution to this to use natural primary keys? I am having a real hard time thinking of a natural primary key for this bunch of users. The problem is they are all young people so they do not have national insurance numbers or any other unique identifier I can think of. I could create a multi-column primary key but there is still a chance, however miniscule of duplicates occurring. Does anyone know of a solution? Thanks

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• Rails named_scope across multiple tables

  - by wakiki

  I'm trying to tidy up my code by using named_scopes in Rails 2.3.x but where I'm struggling with the has_many :through associations. I'm wondering if I'm putting the scopes in the wrong place... Here's some pseudo code below. The problem is that the :accepted named scope is replicated twice... I could of course call :accepted something different but these are the statuses on the table and it seems wrong to call them something different. Can anyone shed light on whether I'm doing the following correctly or not? I know Rails 3 is out but it's still in beta and it's a big project I'm doing so I can't use it in production yet. class Person < ActiveRecord::Base has_many :connections has_many :contacts, :through => :connections named_scope :accepted, :conditions => ["connections.status = ?", Connection::ACCEPTED] # the :accepted named_scope is duplicated named_scope :accepted, :conditions => ["memberships.status = ?", Membership::ACCEPTED] end class Group < ActiveRecord::Base has_many :memberships has_many :members, :through => :memberships end class Connection < ActiveRecord::Base belongs_to :person belongs_to :contact, :class_name => "Person", :foreign_key => "contact_id" end class Membership < ActiveRecord::Base belongs_to :person belongs_to :group end I'm trying to run something like person.contacts.accepted and group.members.accepted which are two different things. Shouldn't the named_scopes be in the Membership and Connection classes? One solution is to just call the two different named scope something different in the Person class or even to create separate associations (ie. has_many :accepted_members and has_many :accepted_contacts) but it seems hackish and in reality I have many more than just accepted (ie. banned members, ignored connections, pending, requested etc etc)

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• T-SQL Re-Assigning Order Numbering

  - by Meltdown

  Say I have a table with a field called "ordernum" that denotes the order of a given set of rows. Now imagine that I delete one of these rows. What type of query would work best for re-assigning the order numbers so that they remain sequential? Here's an example: id group_id name ordernum active --------------------------------------------------- 0_____0______'Name1'___5__true 1_____0______'Name2'___4__true 2_____0______'Name3'___3__true 3_____1______'Name4'___2__true 4_____1______'Name5'__1__true 5_____1______'Name6'__NULL___false Now if I deleted the column with id='4' how would I reset the values in the 'ordernum' field for that specific group? Is this even possible? Or if I added a new row. (The first time the rows are created they are sorted by date, but then the user has the option to set the order himself.) In my table design I have a column 'active' boolean. If 'active' is set to false, then 'ordernum' is set to NULL. Otherwise it should be given an order number.

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