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  • c++ "interface"-like classes similar to Java?

    - by William the Coderer
    In Java, you can define an interface as a class with no actual code implementation, but only to define the methods that a class must implement. Those types can be passed as parameters to methods and returned from methods. In C++, a pure virtual class can't be used as a parameter or return type, from what I can tell. Any way to mimic Java's interface classes? I have a string class in C++, and several subclasses for different encodings (like UTFxxx, ISOxxx, etc) that derive from the base string class. However, since there are so many different encodings, the base class has no meaningful implementation. But it would serve well as an interface if I could handle it as its own object and calls to that object would call on the correct subclass it was inherited to.

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  • Create categorical variable in R based on range

    - by Stedy
    I have a dataframe with a column of integers that I would like to use as a reference to make a new categorical variable. I want to divide the variable into three groups and set the ranges myself (ie 0-5, 6-10, etc). I tried cut but that divides the variable into groups based on a normal distribution and my data is right skewed. I have also tried to use if/then statements but this outputs a true/false value and I would like to keep my original variable. I am sure that there is a simple way to do this but I cannot seem to figure it out. Any advice on a simple way to do this quickly?

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  • Microsoft chart

    - by user222820
    hi there i am writing a program in c# windows app and i use the microsoft chart component i have 100 string in an array and 100 double in an array and i wanna draw a chart with these arrays but i have a problem it draws chart with 5 or 6 column what shoud i do with this problem string[] dates = new string[100]; double[] values = new double[100]; for (int i = 0; i <= 99; i++) { dates[i] = "1/1/138" + i.ToString(); values[i] = i; } s.Series[0].Points.DataBindXY(dates, values);

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  • simple plot algorithm with autoscale

    - by adrin
    I need to implement a simple plotting component in C#(WPF to be more precise). What i have is a collection of data samples containing time (X axis) and a value (both double types). I have a drawing canvas of a fixed size (Width x Height) and a DrawLine method/function that can draw on it. The problem I am facing now is how do I draw the plot so that it is autoscaled? In other words how do I map the samples I have to actual pixels on my Width x Height canvas?

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  • mysql_fetch_array() not displaying all results

    - by user1666995
    I have a database with a calendar table (each row represents one day) with 4 years of rows (2012, 2013, 2014, 2015). I use the column name calyear for the year. I use the following code to find values for distinct years then display it: $year = mysql_query("SELECT DISTINCT calyear FROM calendar"); while($yeararray = mysql_fetch_array($year)) { echo($yeararray['calyear']."<br />"); } The problem is it only displays the years 2013, 2014, 2015 even though when I use echo(mysql_num_rows($year); it displays the value 4 which I take to mean all 4 years are there. I'm not quite sure where I'm going wrong with this.

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  • What effect does static const have on a namespace member

    - by user144182
    namespace MyNamespace { static const double GasConstant = 1.987; Class MyClass { // constructors, methods, etc. }; }; I previously had GasConstant declared within the MyClass declaration (and had a separate definition in the source file since C++ does not support const initialization of non-integral types). I however need to access it from other files and also logically it seems like it should reside at the namespace level. My questions is, what effect does static const have in this case? Clearly const means I can't assign a new value to GasConstant, but what does a static member at the namespace mean. Is this similar to filescope static effect, where the member is not accessible outside of the unit?

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  • Database design - alternatives for Entity Attribute Value (AEV)

    - by Bob
    Hi, see http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters for similar topic. My question: i want to design a database, that will be used for a production facility of different types of products where each product has its own (number of) parameters. because i want the serial numbers to be in one tabel for overview purposes i have a problem with these different paraeters . One solution could be AEV, but it has its downsides, certainly because we have +- 5 products with every product +- 20.000 serial numbers (records). it looks a bit overkill to me... I just don't know how one could design a database so that you have an attribute in a mastertable that says: 'hey, you could find details of this record in THAT detail-table". 'in a way that you qould easely query the results) currenty i am using Visual Basic & Acces 2007. but i'm going to Visual Basic & MySQL. thanks for your help. Bob

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  • LINQ in SQLite for Windows store app does not have 'ThenBy' to order by multiple columns

    - by user1131657
    I have a Windows 8 store application and I'm using the latest version on SQLite for my database. So I want to return some records from the database and I want to order them by more that one column. However SQLite doesn't seem to have the ThenBy statement? So my LINQ statement is below: from i in connection.Table<MyTable>() where i.Type == type orderby i.Usage_Counter // ThenBy i.ID select i); So how do I sort by multiple columns in SQLite without doing another LINQ statement?

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  • slow record deletion with large ntext values

    - by asking
    I'm having trouble deleting some records via a stored procedure from a table in SQLServer 2008R2 that has ntext columns. The stored proc is timing out and running the query directly takes a very long time. The initial query was a straight "delete from y where x = z" and I've also tried running it in batches of 1000 with transactions but it is still slow and timing out in a stored proc. The majority of the records in the table will not be deleted each time (it's not just a once-off query but will be run other times). The ntext columns are not used in the where clause and I can't change the column types. Any suggestions on the quickest way to delete records with large ntext values? Thanks

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  • Using VirtualMode on a DataGridView when the number of rows/columns isn't known

    - by Nathan Baulch
    I need to display an unknown length sequence of dictionaries with unknown keys efficiently in a data grid. This sequence is the result of a potentially slow LINQ query that could contain any number of results. At first I thought that VirtualMode on DataGridView was what I was looking for but it appears that the number of rows and columns must be known upfront. I tried adding a single row and column then adding more as needed from the CellValueNeeded event but this doesn't work. Is this even possible with VirtualMode? Or do I need to estimate how many rows are visible on the screen and manually build up the rows/columns? And if so, how do I ensure that a vertical scrollbar is present and react appropriately when a user uses it?

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  • W3 Validation errors..

    - by Kyle Sevenoaks
    I have 12 errors, but some are just pure non existent. Doctype: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Here's the error report, but the "duplicate specification of attribute "value"" simply isn't true according to my .tpl: {textfield class="quetext" value="Epost*" onblur="if(this.value=='') this.value='Epost*';" onfocus="if(this.value=='Epost*') this.value='';"} Also, does a textarea require the attribute "rows" and "cols"? I thought that was only for tables? And I don't understand what the two errors at the end mean: Line 586, Column 80: Attribute value redefined... Please help! Thanks :) (Sorry if things chop and change, I'm working on the valdiation now, to tidy up as many errors as possible.)

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  • View artifacts leaking into the model of MVC

    - by Jono
    In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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  • Ajax and sophisticated graphics in Java web-app

    - by EugeneP
    In my opinion WWW will sooner or later come to full-blown AJAX web-sites, so that we wouldn't have page reloads every time you click somewhere. Now I want you to ask this. What tools and frameworks can one use to make a Java Web-application running on Tomcat have AJAX functionality like "in-place, with no page reloading" table sorting by clicking on its column header, multi-tabs that enable opening at once the new screen to the user without reloading a page, saving data in the database without reloading a page, and other similar things that we do not usually see on web pages. That's all should probably be based on AJAX. But how to integrate this AJAX functionality with existing java web-frameworks, let's say Spring MVC? Or maybe there are other frameworks that better suit such needs but that can be integrated with core Spring?

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  • What is the best design for these data base tables?

    - by Mohammed Jamal
    I need to find the best solution to make the DB Normalized with large amount of data expected. My site has a Table Tags (contain key word,id) and also 4 types of data related to this tags table like(articles,resources,jobs,...). The big question is:- for the relation with tags what best solution for optimazaion & query speed? make a table for each relation like: table articlesToTags(ArticleID,TagID) table jobsToTags(jobid,tagid) etc. or put it all in one table like table tagsrelation(tagid,itemid,itemtype) I need your help. Please provide me with articles to help me in this design consider that in future the site can conation new section relate to tag Thanks

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  • javax.servlet import cannot be resolved after moving web servlet

    - by Michael Kjörling
    I have written a small web servlet to run under Tomcat, using Eclipse Helios. In its old, non-source-controlled location, everything was fine, but now I need to add this to our source control system. Moving the old files out of the way, creating a new workspace, setting up the server connection and copying and importing the existing projects into the new workspace all worked fine once I figured out how to do it, but I can't get the servlet to build. Instead, I get a whole bunch of cannot be resolved to a type errors talking about various servlet class types; HttpServlet, HttpServletRequest, ServletException, etc. Another error that is almost certainly related is The import javax.servlet cannot be resolved. I am obviously missing something very basic, but I'm new to this (and not having the terminology really down pat probably doesn't help me Google for an answer). Any suggestions as to what I might be missing would be greatly appreciated.

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  • problem with sql query, variable value not inserting itself.

    - by Kaustubh
    the old query works, the new on doesnt. the android logcat gives me error as: Failure 1: no such column abcname. abcname is the value of a editview that im trying to get from a popup in android. ================OLD QUERY: MapsActivity.myDB.execSQL("INSERT INTO " +MapsActivity.TableName + " (name, user_comment, latitude, longitude) " + " VALUES ('tagName','tagComment','tagLatitude','tagLongitude');"); ================NEW QUERY: MapsActivity.myDB.execSQL("INSERT INTO " +MapsActivity.TableName + " (name, user_comment, latitude, longitude) " + " VALUES ("+tagName +",'tagComment','tagLatitude','tagLongitude');"); what is the problem?

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  • Build SUM based daily record

    - by ximarin
    I have a problem building an aggregate function. Here's my problem: I have a table like this id action day isSum difference 1 ping 2012-01-01 1 500 (this is the sum of the differences from last year) 2 ping 2012-01-01 0 -2 3 ping 2012-01-02 0 1 4 ping 2012-01-03 0 -4 5 ping 2012-01-04 0 -2 6 ping 2012-01-05 0 3 7 ping 2012-01-06 0 2 8 ping 2012-01-01 1 0 (this is the sum of the differences from last year, now for pong) 9 pong 2012-01-01 0 -5 10 pong 2012-01-02 0 2 11 pong 2012-01-03 0 -2 12 pong 2012-01-04 0 -8 13 pong 2012-01-05 0 3 14 pong 2012-01-06 0 4 I now need to select the action, day and the summarized difference since 01-01 for every day, so that my result looks like this action day total ping 2012-01-01 498 ping 2012-01-02 499 ping 2012-01-03 495 ping 2012-01-04 493 ping 2012-01-05 496 ping 2012-01-06 498 pong 2012-01-01 - 5 pong 2012-01-02 - 3 pong 2012-01-03 - 5 pong 2012-01-04 -13 pong 2012-01-05 -10 pong 2012-01-06 - 6 How can I do this? there a are a lot of datasets (~1 million), so the query needs to be pretty cheap. I don't know how the use sum to get daily sums for daily records depending on the action-column.

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  • python decorator to add function to list in current scope

    - by AlexH
    Goal: Make a decorator which can modify the scope that it is used in. If it worked: class Blah(): # or perhaps class Blah(ParentClassWhichMakesThisPossible) def one(self): pass @decorated def two(self): pass Blah.decorated ["two"] Why? I essentially want to write classes which can maintain specific dictionaries of methods, so that I can retrieve lists of available methods of different types on a per class basis. errr..... I want to do this: class RuleClass(ParentClass): @rule def blah(self): pass @rule def kapow(self): pass def shazam(self): class OtherRuleClass(ParentClass): @rule def foo(self): pass def bar(self): pass RuleClass.rules.keys() ["blah", "kapow"] OtherRuleClass.rules.keys() ["foo"]

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  • Protocol buffer deserialization and a dynamically loaded DLL in Compact Framework

    - by cloudraven
    I saw a question related to this on the full framework here. Since it seems to have stayed unresolved for quite a while and this is for the compact framework, I though it would be better to create a new question for it. I want to deserialize types for which I am loading assemblies dynamically (with Assembly.LoadFrom) and I am getting a "Unable to identify known-type for ProtoIncludeAttribute" error. In the related question I mentioned, it was hinted that hooking AppDomain.AssemblyResolve event would help solving the problem. It makes sense for the full framework, but that event is not available in the CF. I wonder if there is a way to do this with CF. The structures I am using look a lot like this and all the classes required for deserialization are loaded from the same Assembly. If the assembly is referenced instead of dynamically loaded it works fine, but fails if done dynamically.

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  • How to handle different roles with different previliges in PHP?

    - by user261002
    I would like to know how we can create different "user Roles" for different users in PHP. example: Administrator can create all types of users, add, view, manipulate data, delete managers, viewers, and workers, etc managers can only create, workers and viewers, can add and view data, workers can't create new users, but can only add data and view data, viewers can only view data that has been added to the DB by workers, managers and administrators. I though its better to use different sessions like : $_SESSION['admin'] $_SESSION['manager'] $_SESSION['worker'] $_SESSION['viewvers'] and for every page check which of them have a true or yes value, but I want to know how do they do it in real and big projects??? is there any other way???

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  • Programmatically create static arrays at compile time in C++

    - by Hippicoder
    One can define a static array at compile time as follows: const std::size_t size = 5; unsigned int list[size] = { 1, 2, 3, 4, 5 }; Question 1 - Is it possible by using various kinds of metaprogramming techniques to assign these values "programmatically" at compile time? Question 2 - Assuming all the values in the array are to be the same barr a few, is it possible to selectively assign values at compile time in a programmatic manner? eg: const std::size_t size = 7; unsigned int list[size] = { 0, 0, 2, 3, 0, 0, 0 }; Solutions using C++0x are welcome The array may be quite large, few hundred elements long The array for now will only consist of POD types It can also be assumed the size of the array will be known beforehand, in a static compile-time compliant manner. Solutions must be in C++ (no script or codegen based solutions)

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  • PHP/MYSQL Trouble Selecting by Primary Key

    - by djs22
    Hi all, So I have a primary key column called key. I'm trying to select the row with key = 1 via this code: $query ="SELECT * FROM Bowlers WHERE key = '1'"; $result = mysql_query($query) or die(mysql_error()); For some reason, I'm getting this result: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'key = '1'' at line 1 The mysql statement works for using other keys, ie WHERE name = 'djs22'. Any ideas?

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  • Search filenames in MySQL database table restricted by filetype?

    - by ju
    Hello I have a MySQL database that I replicate from another server. The database contains a table with this columns ID, FileName and FileSize In the table there are more than 4'000'000 records. I want to make fast a search in FileName (varchar) column I found that I can use for this Sphinx search engine. The problem is that I want to restrict searches by filetype. Do I have to and how (trigers?) to extract file extensions for all rows? May be I have to create another table (because this one is replicated) and join them in 1:1 relation? Can you give me some advices please :)

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  • How can I bind dynamic data to DataGridTemplateColumn in code?

    - by TuomoT
    I'm using DataGrid from CodePlex. I have objects (ICustomTypeDescriptor) that have properties 'name' 'description' 'c' 'd' and so on (the names are dynamic, and so is the value) and they have information behind them. I have templates for different types. And if I have to list the properties of a single element I can just bind to the values in xaml and use datatemplateselector (in datagridtemplatecolumn) which will pick the correct template. However, when I'm listing several of the elements, how can I use the selectors and the templates? How do I get the correct property bound to the template (two-way)? When ignoring the need for different templates, using DataGridTextColumn with bindings is very simple (and works, see example below), is there any way to use similar approach with the DataGridTemplateColumn? foreach (String propertyName in listOfPropertyNames) { DataGridTextColumn textColumn = new DataGridTextColumn() { Header = propertyName, Binding = new Binding() { Path = new PropertyPath(propertyName) } }; DataGrid.Columns.Add(textColumn); }

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  • How to return focus from GridView or DataGrid to other control on the page

    - by Senthilkumar
    I Want to know how to focus to control after completing tab navigation for the grid view. I have certain controls in my page and GridView/DataGrid as last control, when I navigate (Tab key navigation) on my page. I can navigate from first control to GridView but when I finish all editable items in grid the tab control goes to browser address bar. I need this should focus to again first control on the page. My question is how can I do this? If it is an ordinary controls then I can use (on key down) attribute of the same.. here how can I get access to the last row's last column on the grid view.

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