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  • C++ template typedef

    - by Notinlist
    I have a class template<size_t N, size_t M> class Matrix { // .... }; I want to make a typedef which creates a Vector (column vector) which is equivalent to a Matrix with sizes N and 1. Something like that: typedef Matrix<N,1> Vector<N>; Which produces compile error. The following creates something similar, but not exactly what I want: template <int N> class Vector: public Matrix<N,1> { }; Is there a solution or a not too expensive workaround / best-practice for it? Thanks in advance!

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  • new with exception with Microsoft

    - by wsd
    As I'm coding for both Windows and Linux, I have a whole host of problems. Microsoft Visual C++ has no stdint header, but for that I wrote my own. Now I found out that MS C++'s new operator does not throw an exception, so I want to fix this a quickly as possible. I know I can define a Macro with Parameters in Parenthesis, can I define a macro that replaces MyClass x = new MyClass(); with #ifdef MSC_VER if(!(MyClass x = new MyClass()) { throw new std::bad_alloc(); } #else MyClass x = new MyClass(); #endif (or something equivalent), AND works in BOTH MS C++ and G++ ? Or alternatively if that is not possible, a batch file to run over the Code to do this? I have become rather dependent on this exception being thrown.

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  • SQL Server JOIN with optional NULL values

    - by Paul McLoughlin
    Imagine that we have two tables as follows: Trades ( TradeRef INT NOT NULL, TradeStatus INT NOT NULL, Broker INT NOT NULL, Country VARCHAR(3) NOT NULL ) CTMBroker ( Broker INT NOT NULL, Country VARCHAR(3) NULL ) (These have been simplified for the purpose of this example). Now, if we wish to join these two tables on the Broker column, and if a country exists in the CTMBroker table on the Country, we have the following two choices: SELECT T.TradeRef,T.TradeStatus FROM Trades AS T JOIN CTMBroker AS B ON B.Broker=T.Broker AND ISNULL(B.Country, T.Country) = T.Country or SELECT T.TradeRef,T.TradeStatus FROM Trades AS T JOIN CTMBroker AS B ON B.Broker=T.Broker AND (B.COUNTRY=T.Country OR B.Country IS NULL) These are both logically equivalent, however in this specific circumstance for our database (SQL Server 2008, SP1) two different execution plans are produced for these two queries with the second version significantly outperforming the first version in terms of both time and logical reads. My question really is as follows: as a general rule would (2) be preferred to (1), or does this just happen to be exploiting some particular idiosyncracy of the optimiser in 2008 SP1 (that could therefore change with future versions of SQL Server).

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  • C#: Oracle Data Type Equivalence with OracleDbType

    - by Partial
    Situation: I am creating an app in C# that uses Oracle.DataAccess.Client (11g) to do certain operations on a Oracle database with stored procedures. I am aware that there is a certain enum (OracleDbType) that contains the Oracle data types, but I am not sure which one to use for certain types. Questions: What is the equivalent Oracle PL/SQL data type for each enumerated type in the OracleDbType enumeration? There are three types of integer (Int16, Int32, Int64) in the OracleDbType... how to know which one to use or are they all suppose to work?

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  • CodeIgniter Question: How to delete records using ActiveRecord with mySQL function as WHERE conditio

    - by Jhourlad Estrella
    I have a table named ChatSessions where I keep track of active users in the chatroom. I need to prune expired user sessions from the table every 10 minutes. Using pure php-mysql is plain simple but I'm totally clueless how to convert this into ActiveRecord in CodeIgniter. The plain SQL query is below: SELECT * FROM `ChatSessions` WHERE `SessionExpires` < DATE_SUB( NOW( ) , INTERVAL 10 MINUTE ) Can anybody tell me what is the equivalent code in CodeIgniter using ActiveRecord? Thanks in advanced.

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  • Instance where embedded C++ compilers don't support multiple inheritance?

    - by Nathan
    I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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  • Handling Messages in Console Apps/DLLs in C++ Win32

    - by vsimon
    I would like to have the ability to process Win32 messages in a console app and/or inside a standalone DLL. I have been able to do it in .NET with the following article and it works great in C# inside a console app and standalone DLL http://msdn.microsoft.com/en-us/magazine/cc163417.aspx Is there a way to do the equivalent with C/C++ Win32 APIs? I have tried doing RegisterClassEx(...) and CreateWindow(...) even passing in HWND_MESSAGE to hWndParent but the trouble is that after the "invisible" window is created messages are not being processed probably due to the lack of a message pump. Where would the message pump go if you had a DLL entry point? I have tried creating another thread in a DLL and put while(GetMesage(..)) there but that did not work either. Any ideas?

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  • replacing data.frame element-wise operations with data.table (that used rowname)

    - by Harold
    So lets say I have the following data.frames: df1 <- data.frame(y = 1:10, z = rnorm(10), row.names = letters[1:10]) df2 <- data.frame(y = c(rep(2, 5), rep(5, 5)), z = rnorm(10), row.names = letters[1:10]) And perhaps the "equivalent" data.tables: dt1 <- data.table(x = rownames(df1), df1, key = 'x') dt2 <- data.table(x = rownames(df2), df2, key = 'x') If I want to do element-wise operations between df1 and df2, they look something like dfRes <- df1 / df2 And rownames() is preserved: R> head(dfRes) y z a 0.5 3.1405463 b 1.0 1.2925200 c 1.5 1.4137930 d 2.0 -0.5532855 e 2.5 -0.0998303 f 1.2 -1.6236294 My poor understanding of data.table says the same operation should look like this: dtRes <- dt1[, !'x', with = F] / dt2[, !'x', with = F] dtRes[, x := dt1[,x,]] setkey(dtRes, x) (setkey optional) Is there a more data.table-esque way of doing this? As a slightly related aside, more generally, I would have other columns such as factors in each data.table and I would like to omit those columns while doing the element-wise operations, but still have them in the result. Does this make sense? Thanks!

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  • SSRS Issue: Rounding to nearest .25

    - by D.R.
    I have an SSRS (2008) report that takes in a raw transactions, then groups and totals them. At the "Total" level, I would like to round the final numbers to the nearest .25, however I cannot find a method to do this. According to what I've read, the Round() function in SSRS only rounds to integers. I have found a couple ways to do it in SQL, but the problem is, I want to do all the calculations with the REAL numbers and just round the result so that I don't introduce a significant amount of error from the real numbers. Here's the best SQL solution I could find: dec(round(number * 4, 0)/4,11,2) as Nearest_Qtr Anyone know how I could do the equivalent in the actual SSRS report? Thanks in advance for the help!

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  • How to write custom SQLite functions in Javascript inside a Webkit browser?

    - by Jay Godse
    I have just learned how to use the SQLite database for local storage in a Webkit web browser (e.g. Google Chrome or Apple Safari) using the Javascript API. For example the "Sticky Notes" application. However, I know that SQLite has a function called sqlite_create_function() that lets you add custom functions to your instance of SQLite on the fly which can then be used inside SQL queries. This function is described at sqlite.org. I also know that you can call an equivalent of this API in Ruby as described here. QUESTION: Can anybody show me how to do this in Javascript - i.e. write a custom function in Javascript that can be bound into the SQLite database at run time to be called by the SQLite engine, and all inside a Webkit browser?

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  • Ping or otherwise tell if a device is on the network by MAC in C#

    - by Aric TenEyck
    I'm developing a home security application. One thing I'd like to do is automatically turn it off and on based on whether or not I'm at home. I have a phone with Wifi that automatically connects to my network when I'm home. The phone connects and gets its address via DHCP. While I could configure it to use a static IP, I'd rather not. Is there any kind of 'Ping' or equivalent in C# / .Net that can take the MAC address of a device and tell me whether or not it's currently active on the network?

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  • Counting bits set in a .Net BitArray Class

    - by Sam
    I am implementing a library where I am extensively using the .Net BitArray class and need an equivalent to the Java BitSet.Cardinality() method, i.e. a method which returns the number of bits set. I was thinking of implementing it as an extension method for the BitArray class. The trivial implementation is to iterate and count the bits set (like below), but I wanted a faster implementation as I would be performing thousands of set operations and counting the answer. Is there a faster way than the example below? count = 0; for (int i = 0; i < mybitarray.Length; i++) { if (mybitarray [i]) count++; }

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  • How to declare a variable that spans multiple lines

    - by Chris Wilson
    I'm attempting to initialise a string variable in C++, and the value is so long that it's going to exceed the 80 character per line limit I'm working to, so I'd like to split it to the next line, but I'm not sure how to do that. I know that when splitting the contents of a stream across multiple lines, the syntax goes like cout << "This is a string" << "This is another string"; Is there an equivalent for variable assignment, or do I have to declare multiple variables and concatenate them? Edit: I misspoke when I wrote the initial question. When I say 'next line', I'm just meaning the next line of the script. When it is printed upon execution, I would like it to be on the same line.

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  • Build multiple executables with small changes in objects

    - by Morgoth
    Consider the following Makefile COMP = compiler OBJECTS = file1 \ file2 \ file3 \ file4 \ file5_suffix \ file6 \ file7 \ file8 \ file9_suffix \ file10 all: $(OBJECTS) $(COMP) $(OBJECTS) -o bin/executable_suffix Is there an easy way to compile multiple executables for different values of suffix? For example, the equivalent of COMP = compiler OBJECTS1 = file1 \ file2 \ file3 \ file4 \ file5_s1 \ file6 \ file7 \ file8 \ file9_s1 \ file10 OBJECTS2 = file1 \ file2 \ file3 \ file4 \ file5_s2 \ file6 \ file7 \ file8 \ file9_s2 \ file10 all: $(OBJECTS1) $(OBJECTS2) $(COMP) $(OBJECTS1) -o bin/executable_s1 $(COMP) $(OBJECTS2) -o bin/executable_s2 but without redefining the whole list of objects? In the real life case I am dealing with, there might be 50+ objects and a dozen binaries to build, with only small changes between the object list each time, so it would be nice not to have to list all the objects each time.

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  • Returning multiple datasets from a stored proc in VB

    - by Ryan Stephens
    I have an encrypted SQL Server stored proc that I run with (or the vb .net equivalent code of): declare @p4 nvarchar(100) set @p4=NULL declare @p5 bigint set @p5=NULL exec AA_PAY_BACS_EXPORT_RETRIEVE_S @PS_UserId=N'ADMN', @PS_Department=N'', @PS_PayFrequency=2, @PS_ErrorDescription=@p4 output select @p4, @p5 this returns 2 datasets and the output parameters for the results, the datasets are made up of various table joins etc, one holds the header record and one the detail records. I need to get the 2 datasets into a structure in VB .net (e.g. linq, sqldatareader, typed datasets) so that I can code with them, I don't know what tables any of this comes from and there are alot of them Whooopeee!!! I came close using Linq to SQL and IMultipleResults but got frustrated when I had to recode it every time I made a change to the designer file. My feelings are that there must be a simple way to do this, any ideas?

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  • C++ - Print Out Objects From Set

    - by John Smith
    If I have a C++ set, declaration set personList; with iterator, set::const_iterator location; how can I print out the contents of the set? They are all person objects, and I have overridden the operator<< for Person. The line that errors is: cout << location and it's in a basic for loop. Netbeans gives the following error: proj.cpp:78: error: no match for ‘operator<<’ in ‘std::cout << location’ so it looks like it wants an override for the iterator's <<. Basically, I am taking objects that used to be stored in an array format, but are now in a set. What is the equivalent to cout << array[i] for sets?

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  • How do I set ORDER BY params using prepared PDO statement?

    - by Marlorn
    I'm having problems using params in the ORDER BY section of my SQL. It doesn't issue any warnings, but prints out nothing. $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT field from table WHERE column = :my_param ORDER BY :order :direction"); $stmt->bindParam(':my_param', $is_live, PDO::PARAM_STR); $stmt->bindParam(':order', $order, PDO::PARAM_STR); $stmt->bindParam(':direction', $direction, PDO::PARAM_STR); $stmt->execute(); The :my_param works, but not :order or :direction. Is it not being internally escaped correctly? Am I stuck inserting it directly in the SQL? Like so: $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT * from table WHERE is_live = :is_live ORDER BY $order $direction"); Is there a PDO::PARAM_COLUMN_NAME constant or some equivalent? Thanks!

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  • Getting the value from an array in the model in rails

    - by slythic
    Hi all, I have a relatively simple problem. I have a model named Item which I've added a status field. The status field will only have two options (Lost or Found). So I created the following array in my Item model: STATUS = [ [1, "Lost"], [2, "Found"]] In my form view I added the following code which works great: <%= collection_select :item, :status, Item::STATUS, :first, :last, {:include_blank => 'Select status'} %> This stores the numeric id (1 or 2) of the status in the database. However, in my show view I can't figure out how to convert from the numeric id (again, 1 or 2) to the text equivalent of Lost or Found. Any ideas on how to get this to work? Is there a better way to go about this? Many thanks, Tony

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  • Does Apache allow to authorize an HTTP request based on a result of a subrequest?

    - by Jan Wrobel
    I'm looking for an equivalent of nginx http auth request module but for Apache. For each incoming HTTP requests, the module sends a subrequests to authentication/authorization back-end. Th auth request carries a path and all headers of the original request. Based on the result of the auth request, the original requests is allowed (HTTP code 200), denied (HTTP code 403) or login is requested (HTTP code 401). Such a generic mechanism allows to build really flexible authentication and authorization schemes. Is something like this possible in Apache (likely with a help of some third party module)?

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  • Any way to avoid a filesort when order by is different to where clause?

    - by Julian
    I have an incredibly simple query (table type InnoDb) and EXPLAIN says that MySQL must do an extra pass to find out how to retrieve the rows in sorted order. SELECT * FROM `comments` WHERE (commentable_id = 1976) ORDER BY created_at desc LIMIT 0, 5 exact explain output: table select_type type extra possible_keys key key length ref rows comments simple ref using where; using filesort common_lookups common_lookups 5 const 89 commentable_id is indexed. Comments has nothing trick in it, just a content field. The manual suggests that if the order by is different to the where, there is no way filesort can be avoided. http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html I also tried order by id as well as it's equivalent but makes no difference, even if I add id as an index (which I understand is not required as id is indexed implicitly in MySQL). thanks in advance for any ideas!

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  • WPF, convert Path.DataProperty to Segment objects

    - by user275587
    I was wondering if there was a tool to convert a path data like "M 0 0 l 10 10" to it's equivalent line/curve segment code. Currently I'm using: string pathXaml = "<Path xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\" xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\" Data=\"M 0 0 l 10 10\"/>"; Path path = (Path)System.Windows.Markup.XamlReader.Load(pathXaml); It appears to me that calling XamlParser is much slower than explicitly creating the line segments. However converting a lot of paths by hand is very tedious.

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  • Is there a shorthand way to denullify a string in C#?

    - by Moose Factory
    Is there a shorthand way to denullify a string in C#? It would be the equivalent of (if 'x' is a string): string y = x == null ? "" : x; I guess I'm hoping there's some operator that would work something like: string y = #x; Wishful thinking, huh? The closest I've got so far is an extension method on the string class: public static string ToNotNull(this string value) { return value == null ? "" : value; } which allows me to do: string y = x.ToNotNull(); Any improvements on that, anyone?

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  • I want absolute atomicity on a single couchdb instance (insert, fail if already existing)

    - by MatternPatching
    I've come to really love the couchdb style of organizing and updating data, but there are a few situations where I really need to be able to create an entry and determine if an equivalent entry is already in existence before returning to the user. The only situation that this is absolutely necessary for my application is user registration. I'm fine with having all user registration writes go to a particular, designated couchdb instance known as the "registration-instance". I want to hash the user_id into some _id to use. Then execute a put with this _id, but fail if the _id is already inserted. I need to return to the user that the user name is already reserved, and I cannot detect the conflict later and resolve it at that point, because the user would be under the impression that they had reserved the user name. I don't see why couchdb couldn't provide some way to do this, under the assumption that you designate that inserts for a particular "type" of document always are routed to a particular instance.

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  • Want to understand C++ sentry object

    - by Romain Hippeau
    I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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  • C/C++ memory usage API in Linux/Windows

    - by minjang
    I'd like to obtain memory usage information for both per process and system wide. In Windows, it's pretty easy. GetProcessMemoryInfo and GlobalMemoryStatusEx do these jobs greatly and very easily. For example, GetProcessMemoryInfo gives "PeakWorkingSetSize" of the given process. GlobalMemoryStatusEx returns system wide available memory. However, I need to do it on Linux. I'm trying to find Linux system APIs that are equivalent GetProcessMemoryInfo and GlobalMemoryStatusEx. I found 'getrusage'. However, max 'ru_maxrss' (resident set size) in struct rusage is just zero, which is not implemented. Also, I have no idea to get system-wide free memory. Current workaround for it, I'm using "system("ps -p %my_pid -o vsz,rsz");". Manually logging to the file. But, it's dirty and not convenient to process the data. I'd like to know some fancy Linux APIs for this purpose.

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