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• Top x rows and group by (again)

  - by Tibor Szasz

  Hello, I know it's a frequent question but I just can't figure it out and the examples I found didn't helped. What I learned, the best strategy is to try to find the top and bottom values of the top range and then select the rest, but implementing is a bit tricky. Example table: id | title | group_id | votes I'd like to get the top 3 voted rows from the table, for each group. I'm expecting this result: 91 | hello1 | 1 | 10 28 | hello2 | 1 | 9 73 | hello3 | 1 | 8 84 | hello4 | 2 | 456 58 | hello5 | 2 | 11 56 | hello6 | 2 | 0 17 | hello7 | 3 | 50 78 | hello8 | 3 | 9 99 | hello9 | 3 | 1 I've fond complex queries and examples, but they didn't really helped.

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• Passing objects by reference or not in C#

  - by Piku

  Suppose I have a class like this: public class ThingManager { List<SomeClass> ItemList; public void AddToList (SomeClass Item) { ItemList.Add(Item); } public void ProcessListItems() { // go through list one item at a time, get item from list, // modify item according to class' purpose } } Assume "SomeClass" is a fairly large class containing methods and members that are quite complex (List<s and arrays, for example) and that there may be a large quantity of them, so not copying vast amounts of data around the program is important. Should the "AddToList" method have "ref" in it or not? And why? It's like trying to learn pointers in C all over again ;-) (which is probably why I am getting confused, I'm trying to relate these to pointers. In C it'd be "SomeClass *Item" and a list of "SomeClass *" variables)

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• How to disable UI control based on domain object's state?

  - by Subb

  Here's my problem. I have a somewhat complex domain object, which, depending on its state, responds to certain actions. I think the state pattern is pretty much the solution for that. However, I need to display which actions are possible at any moment in the UI. Ex: The domain object is an audio player. Some songs can't be skipped (like ads), so I need to disable the "next" and "previous" buttons in the GUI so the user have some kind of feedback of which action he can execute. I've looked at Swing's Action class (note: this is not a Java project), but I think I would need to keep every Actions in my domain object class (audio player), so it can enable or disable them depending on its own state (thus, affecting the UI). Is it the way to do it?

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• Best practice for partial updates in a RESTful service

  - by magiconair

  I am writing a RESTful service for a customer management system and I am trying to find the best practice for updating records partially. For example, I want the caller to be able to read the full record with a GET request. But for updating it only certain operations on the record are allowed, like change the status from ENABLED to DISABLED. (I have more complex scenarios than this) I don't want the caller to submit the entire record with just the updated field for security reasons (it also feels like overkill). Is there a recommended way of constructing the URIs? Do I use GET, POST, PUT or is there no agreed way of doing these kind of things? When reading the REST books RPC style calls seem to be frowned upon. Thanks Frank

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• Using named_scope with counts of child models

  - by Joe Cairns

  Hi, I have a simple parent object having many children. I'm trying to figure out how to use a named scope for bringing back just parents with specific numbers of children. Is this possible? class Foo < ActiveRecord::Base has_many :bars named_scope :with_no_bars, ... # count of bars == 0 named_scope :with_one_bar, ... # count of bars == 1 named_scope :with_more_than_one_bar, ... # count of bars > 1 end class Bar < ActiveRecord::Base belongs_to :foo end I'm hoping to do something like Foo.with_one_bar I could write methods on the parent class for something like this, but I'd rather have the power of the named scope

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• Bash or python for changing spacing in files

  - by Werner

  Hi, I have a set of 10000 files. In all of them, the second line, looks like: AAA 3.429 3.84 so there is just one space (requirement) between AAA and the two other columns. The rest of lines on each file are completely different and correspond to 10 columns of numbers. Randomly, in around 20% of the files, and due to some errors, one gets BBB 3.429 3.84 so now there are two spaces between the first and second column. This is a big error so I need to fix it, changing from 2 to 1 space in the files where the error takes place. The first approach I thought of was to write a bash script that for each file reads the 3 values of the second line and then prints them with just one space, doing it for all the files. I wonder what do oyu think about this approach and if you could suggest something better, bashm python or someother approach. Thanks

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• Transform PDF to HTML, keep layout

  - by Tgr

  What methods are there to transform a PDF to HTML? It could be anything - online service, software, library. (Opensource preferred. In the last case, php or python would be preferred.) It has to keep the original layout (including page numbers, footnotes and such), keep the images (combining them to one single background image per page is acceptable) and keep the links. It should preferably output valid XHTML and clean up PDF features such as ligatures, but if there is some post-processing required, I can live with that. Something with a clean, relatively semantic HTML output would be great. The closest one I found was zamzar.org, but it choked on links. (Also, the HTML output is an ugly heap of absolutely positioned divs and needs post-processing because of encoding problems.)

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• Does any faster centralized version control than SVN exists?

  - by Savageman

  Hello, I've been using SVN since a long time and now we're trying on Git. I'm not talking on the centralized / decentralized debate here. My only concern is speed. The latter tool is much faster. But sometimes, I NEED to work with a centralized approach, which is much more simple and less complex than the decentralized one. The learning curve is really fast, which saves a lot of time (while digging into decentralized would lead to a waste of time, given the learning curve is much longer and we encounter more problem when working with it). However, SVN is really slow compared to GIT, and I don't think it has anything to do with the centralized argument. Decentralized systems also have to deal with server connections and file transfert. So I can easilly imagine a faster implementation of centralized version control could exists. Does someone has any clue on this?

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• Nested sql queries in rails when :has_and_belongst_to_many

  - by Godisemo

  Hello, In my application I the next task that has not already been done by a user. I have Three models, A Book that has many Tasks and then I have a User that has has and belongs to many tasks. The table tasks_users table contains all completed tasks so I need to write a complex query to find the next task to perform. I have came up with two solutions in pure SQL that works, but I cant translate them to rails, thats what I need help with SELECT * FROM `tasks` WHERE `tasks`.`book_id` = @book_id AND `tasks`.`id` NOT IN ( SELECT `tasks_users`.`task_id` FROM `tasks_users` WHERE `tasks_users`.`user_id` = @user_id) ORDER BY `task`.`date` ASC LIMIT 1; and equally without nested select SELECT * FROM tasks LEFT JOIN tasks_users ON tasks_users.tasks_id = task.id AND tasks_users.user_id = @user_id WHERE tasks_users.task_id IS NULL AND tasks.book_id = @book_id LIMIT 1; This is what I Have done in rails with the MetaWhere plugin book.tasks.joins(:users.outer).where(:users => {:id => nil}) but I cant figure out how to get the current user there too, Thanks for any help!

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• Comparing numeric strings

  - by Kiren Siva

  From the question PHP Type-Juggling and (strict) Greater/Lesser Than Comparisons I know PHP interpret strings as numbers whenever it can. "10" < "1a" => 10 less than 1 expecting false "1a" < "2" => 1 less than 2 expecting true "10" > "2" => 10 greater than 2 expecting true But in the case of "10" < "1a" php returns true. I am not understanding the concept please help me to clarify it. Edit: But when I add "10" + "1a" it returns 11 that means php interprets "10" as 10 and "1a" as 1. Is that correct?

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• What is the maximum number of controls that a VBA form can hold?

  - by Lunatik

  I'm currently building an Excel 2003 app that requires a horribly complex form and am worried about limitations on the number of controls. It currently has 154 controls (counted using Me.Controls.Count - this should be accurate, right?) but is probably only about a third complete. The workflow really fits a single form, but I guess I can split it up if I really have to. I see evidence in a Google search that VB6 (this usually includes VBA) has a hard limit of 254 controls in a form. However, I created a dummy form with well over 1200 controls which still loaded and appeared to work just fine. I did get some 'out of memory' errors when trying to add specific combinations of controls though, say 800 buttons and 150 labels, leading me to think that any limit might be affected by the memory requirements of each type of control. Does anyone have any information that might help ensure that I or, more importantly, other users with differing environments don't run into any memory issues with such a large form?

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• C# dealing with invalid user input

  - by Zka

  Have a simple console app where user is asked for several values to input. Input is read via console.readline(). Ex Name: Fred //string Lastname: Ashcloud //string Age: 28 //int I would like to make sure that int and double types are entered and if the user enters garbage, lets him repeat the procedure. Example, if the user enters "28 years old" where age expects int the app will crash. What is the best way to check for these inputs? Right now I can only think of: while (!Int32.TryParse(text, out number)) { Console.WriteLine("Error write only numbers"); text = Console.ReadLine(); } Is there any other way to do this? try catch statements if one wants to give a more detailed feedback to the user? How in that case?

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• Formatting a query to enumerate through 2 different datatables

  - by boiler1974

  I have 2 datatables sendTable and recvTable They both have identical column names and numbers of columns "NODE" "DSP Name" "BUS" "IDENT" "STATION" "REF1" "REF2" "REF3" "REF4" "REF5" "REF6" "REF7" "REF8" I need to compare these 2 tables and separate out the mismatches I only need to check Columns 3-11 and Ignore col 1 and 2 I tried at first removing the 2 columns and then loop thru row by row and return matches and mismatches but the problem with this approach is that I no longer have the "NODE" and "DSP Name" associated with the row when I finalize my results So I need help with a query Here is my attempt var samerecordQuery = from r1 in sendTable.AsEnumerable() where r1.Field<int>("BUS").Equals(from r2 in recvTable.AsEnumerable() where r2.Field<int>("BUS")) this obviously doesn't work so how do I format the query to say from r1 cols[3-11] equals r2 cols [3-11] and once I have this I can use the except to pull out the mismatches

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• Adding global blank option to DroDownList in MVC

  - by Diegos Grace

  Is there a way of using a templated helper in mvc so that each and every select list in my project has a custom default 'Choose an option' with null value etc. The posts I have seen seem a little complex, is it possible to have a DropDownList.ascx file in shared view folder with something like this: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<SelectListItem>>" %> <%= Html.DropDownList(selectlist name, selectlist value, "Choose an option")%> And then having a UIHint("DropDownList") for each dropdownlist in the ViewModel? Some guidance on syntax of parameters would be much appreciated, where name and value of the viewmodel dropdownlist plus the 'Choose an option' string are passed. Or is this all wishful thinking?

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• MySQL Rank Not Matching High Score in Table

  - by boddie

  While making a game the MySQL call to get the top 10 is as follows: SELECT username, score FROM userinfo ORDER BY score DESC LIMIT 10 This seems to work decently enough, but when paired with a call to get a individual player's rank the numbers may be different if the player has a tied score with other players. The call to get the players rank is as follows: SELECT (SELECT COUNT(*) FROM userinfo ui WHERE (ui.score, ui.username) >= (uo.score, uo.username)) AS rank FROM userinfo uo WHERE username='boddie'; Example results from first call: +------------+-------+ | username | score | +------------+-------+ | admin | 4878 | | test3 | 3456 | | char | 785 | | test2 | 456 | | test1 | 253 | | test4 | 78 | | test7 | 0 | | boddie | 0 | | Lz | 0 | | char1 | 0 | +------------+-------+ Example results from second call +------+ | rank | +------+ | 10 | +------+ As can be seen, the first call ranks the player at number 8 on the list, but the second call puts him at number 10. What changes or what can I do to make these calls give matching results? Thank you in advance for any help!

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• Memory address of a variable

  - by dotnetvoyager

  Hi Everyone, Is it possible to get the memory address of a variable in C#. What I am trying to do is very simple. I want to declare variables of type Double, Float, Decimal and assign the value 1.1 to each of these variables. Then I would like to go and see how these values are represented in memory. I need to get the memory address of the variable in order to see how its stored in memory. Once I have the memory address I plan to put a break point in the code and use the Debug - Windows - Memory option in visual studio to see how the numbers are stored in memory. Cheers,

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• Efficiently generate a 16-character, alphanumeric string

  - by ensnare

  I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table. Would something like this work? def genKey(): hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64") alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash) return alnum_hash[:16] What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances. Or is there a better way to do all this? Thanks.

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• Math - Adding with PHP

  - by Wayne

  Basically I can't get it right. I need something like this: if($p == 1) { $start = 0; $limit = 16; } The numbers must add on depending on the value of the $p, e.g. if $p is 5 then the values of $start and $limit would be: if($p == 5) { $start = 64; $limit = 80; } The math is to add 16, depending on the value of $p. Thanks.

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• problem with hierarchical clustering in Python

  - by user248237

  I am doing a hierarchical clustering a 2 dimensional matrix by correlation distance metric (i.e. 1 - Pearson correlation). My code is the following (the data is in a variable called "data"): from hcluster import * Y = pdist(data, 'correlation') cluster_type = 'average' Z = linkage(Y, cluster_type) dendrogram(Z) The error I get is: ValueError: Linkage 'Z' contains negative distances. What causes this error? The matrix "data" that I use is simply: [[ 156.651968 2345.168618] [ 158.089968 2032.840106] [ 207.996413 2786.779081] [ 151.885804 2286.70533 ] [ 154.33665 1967.74431 ] [ 150.060182 1931.991169] [ 133.800787 1978.539644] [ 112.743217 1478.903191] [ 125.388905 1422.3247 ]] I don't see how pdist could ever produce negative numbers when taking 1 - pearson correlation. Any ideas on this? thank you.

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• How to learn to program C the right way

  - by sfactor

  i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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• Sql query: use where in or foreach?

  - by phenevo

  Hi, I'm using query, where the piece is: ...where code in ('va1','var2'...') I have about 50k of this codes. It was working when I has 30k codes, but know I get: The query processor ran out of internal resources and could not produce a query plan. This is a rare event and only expected for extremely complex queries or queries that reference a very large number of tables or partition I think that problem is related with IN... So now I'm planning use foreach(string code in codes) ...where code =code Is it good Idea ??

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• Why does this give a segmentation fault?

  - by nightcracker

  I'm stunned, why does this code give me a segmentation fault? #include <stdio.h> #define LIMIT 1500000 typedef struct { int p; int a; int b; } triplet; int main(int argc, char **argv) { int i; triplet triplets[LIMIT]; for (i = 0; i < 5; i++) { triplets[i].p = 9; // remove this line and everything works fine } printf("%d\n", triplets[15].p); return 0; } EDIT: After changing LIMIT to 150 I no longer get a segmentation fault, it prints random numbers instead.

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• PHP While Loops from Arrays

  - by Michael

  I have a table that contains members names and a field with multiple ID numbers. I want to create a query that returns results where any values in the ID fields overlap with any values in the array. For example: lastname: Smith firstname: John id: 101, 103 I have Array #1 with the values 101, 102, 103 I want the query to output all members who have the values 101 or 102 or 103 listed in their id field with multiple ids listed. Array ( [0] => 101 [1] => 102 [2] => 103 ) $sql="SELECT firstname, lastname, id FROM members WHERE id LIKE '%".$array_num_1."%'"; $result=mysql_query($sql); while ($rows=mysql_fetch_array($result)) { echo $rows['lastname'].', '.$rows['firstname'].'-'.$rows['id']; }

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• Get only new RSS entries with PHP Script ?

  - by ArneRie

  What im trying to do: Fetch X numbers of RSS Feeds from my Blogs and echo only new entries. My Problem is, how to know wich items are already parsed? Solution so far: Fetch the Feed every 5 hours, store all titles inside an Database table or flat file. Next run check if the title is already in database if not print it and save it inside the database. But iam not sure if this is best practise to do this? If someone knows a fast way, it would be great. Sorry for my poor english.

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• What's the best technology for a medium complexity web application?

  - by naveed

  I'm planning to work on a web application of reasonable complexity and am wondering what technology to go with. It will probably start with one person, but there will be 2 or 3 more eventually. My first requirement is to be able to do this as quickly as possible - preferably with as less code as possible. Secondly requirement is that it should be able to scale easily. I have worked with .NET and PHP. So, I am thinking about ASP .NET MVC or CakePHP. It appears to me that CakePHP might be quicker. I did look at Ruby on Rails, but the learning curve is a little steep (which is not an issue if I can be convinced that this is the best tool for the task), I'm not too crazy about the huge number of files generated and I have heard about scalability issues as well as it's applicability to complex situations. I look forward to your opinions on your favorite technology and why.

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