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  • When accessing ResultSets in JDBC, is there an elegant way to distinguish between nulls and actual z

    - by Uri
    When using JDBC and accessing primitive types via a result set, is there a more elegant way to deal with the null/0 than the following: int myInt = rs.getInt(columnNumber) if(rs.wasNull())? { // Treat as null } else { // Treat as 0 } I personally cringe whenever I see this sort of code. I fail to see why ResultSet was not defined to return the boxed integer types (except, perhaps, performance) or at least provide both. Bonus points if anyone can convince me that the current API design is great :) My solution was to write a wrapper that returns an Integer (I care more about elegance of client code than performance), but I'm wondering if I'm missing a better way to do this.

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  • Better way to write an object generator for an RAII template class?

    - by Dan
    I would like to write an object generator for a templated RAII class -- basically a function template to construct an object using type deduction of parameters so the types don't have to be specified explicitly. The problem I foresee is that the helper function that takes care of type deduction for me is going to return the object by value, which will result in a premature call to the RAII destructor when the copy is made. Perhaps C++0x move semantics could help but that's not an option for me. Anyone seen this problem before and have a good solution? This is what I have: template<typename T, typename U, typename V> class FooAdder { private: typedef OtherThing<T, U, V> Thing; Thing &thing_; int a_; // many other members public: FooAdder(Thing &thing, int a); ~FooAdder(); void foo(T t, U u); void bar(V v); }; The gist is that OtherThing has a horrible interface, and FooAdder is supposed to make it easier to use. The intended use is roughly like this: FooAdder(myThing, 2) .foo(3, 4) .foo(5, 6) .bar(7) .foo(8, 9); The FooAdder constructor initializes some internal data structures. The foo and bar methods populate those data structures. The ~FooAdder dtor wraps things up and calls a method on thing_, taking care of all the nastiness. That would work fine if FooAdder wasn't a template. But since it is, I would need to put the types in, more like this: FooAdder<Abc, Def, Ghi>(myThing, 2) ... That's annoying, because the types can be inferred based on myThing. So I would prefer to create a templated object generator, similar to std::make_pair, that will do the type deduction for me. Something like this: template<typename T, typename U, typename V> FooAdder<T, U, V> AddFoo(Thing &thing, int a) { return FooAdder<T, U, V>(thing, a); } That seems problematic: because it returns by value, the stack temporary object will be destructed, which will cause the RAII dtor to run prematurely. One thought I had was to give FooAdder a copy ctor with move semantics, kinda like std::auto_ptr. But I would like to do this without dynamic memory allocation, so I thought the copy ctor could set a flag within FooAdder indicating the dtor shouldn't do the wrap-up. Like this: FooAdder(FooAdder &rhs) // Note: rhs is not const : thing_(rhs.thing_) , a_(rhs.a_) , // etc... lots of other members, annoying. , moved(false) { rhs.moved = true; } ~FooAdder() { if (!moved) { // do whatever it would have done } } Seems clunky. Anyone got a better way?

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  • Should every class have its own namespace?

    - by thehouse
    Something that has been troubling me for a while: The current wisdom is that types should be kept in a namespace that only contains functions which are part of the type's non-member interface (see C++ Coding Standards Sutter and Alexandrescu or here) to prevent ADL pulling in unrelated definitions. Does this imply that all classes must have a namespace of their own? If we assume that a class may be augmented in the future by the addition of non-member functions, then it can never be safe to put two types in the same namespace as either one of them may introduce non-member functions that could interfere with the other. The reason I ask is that namespaces are becoming cumbersome for me. I'm writing a header-only library and I find myself using classes names such as project::component::class_name::class_name. Their implementations call helper functions but as these can't be in the same namespace they also have to be fully qualified!

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  • What should be contained in a global Subversion ignore pattern for Visual Studio 2010?

    - by Chris Simmons
    After installing and using Visual Studio 2010, I'm seeing some newer file types (at least with C++ projects ... don't know about the other types) as compared to 2008. e.g. .sdf, .opensdf, which I guess are the replacement for ncb files with Intellisense info stored in SQL Server Compact files? I also notice .log files are generated, which appear to be build logs. Given this, what's safe to add to my global ignore pattern? Off the bat, I'd assume .sdf, .opensdf, but what else?

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  • Can using non primitive Integer/ Long datatypes too frequently in the application, hurt the performance??

    - by Marcos
    I am using Long/Integer data types very frequently in my application, to build Generic datatypes. I fear that using these wrapper objects instead of primitive data types may be harmful for performance since each time it needs to create objects which is an expensive operation. but also it seems that I have no other choice(when I have to use primtives with generics) rather than just using them. However, still it would be great if you can suggest if there is anything I could do to make it better. or any way if I could just avoid it ?? Also What may be the downsides of this ? Suggestions welcomed!

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  • [Java6] Same source code, Eclipse build success but Maven (javac) fails

    - by EnToutCas
    Keep getting this error when compiling using Maven: type parameters of <X>X cannot be determined; no unique maximal instance exists for type variable X with upper bounds int,java.lang.Object Generics type interference cannot be applied to primitive types. But I thought since Java5, boxing/unboxing mechanism works seamlessly between primitive types and wrapper classes. In any case, the strange thing is Eclipse doesn't report any errors and happily compiles. I'm using JDK1.6.0_12. What could possibly be the problem here?

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  • How should I synchronize lists in WCF?

    - by mafutrct
    I've got a WCF service that offers multiple lists of items of different types. The lists can be changed on the server. Every change has to be published to all clients to make sure every client has an up-to-date copy of each server list. Currently I'm using this strategy: On login, every client receives the current status of every list. On every change, the added or removed item is sent to all clients. The drawback is that I have to create a callback for every list, since the items are of different types. Is there a pattern I could apply? Or do I really have to duplicate code for each of the lists?

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  • Get count matches in query on large table very slow

    - by Roy Roes
    I have a mysql table "items" with 2 integer fields: seid and tiid The table has about 35000000 records, so it's very large. seid tiid ----------- 1 1 2 2 2 3 2 4 3 4 4 1 4 2 The table has a primary key on both fields, an index on seid and an index on tiid. Someone types in 1 or more tiid values and now I would like to get the seid with most results. For example when someone types 1,2,3, I would like to get seid 2 and 4 as result. They both have 2 matches on the tiid values. My query so far: SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid HAVING c = (SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid ORDER BY c DESC LIMIT 1) But this query is extremly slow, because of the large table. Does anyone know how to construct a better query for this purpose?

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  • PreparedStatement and 'null' value in WHERE clause

    - by bond
    I am using PrepareStatement and BatchUpdate for executimg a UPDATE query. In for loop I create a Batch. At end of loop I execute batch. Above logic works fine if SQL query used in PrepareStatement does not have null values in WHERE claues. Update Statement fails if there is null value in WHERE clasue. My code looks something like this, connection = getConnection(); PreparedStatement ps = connection.prepareStatement("UPDATE TEST_TABLE SET Col1 = true WHERE Col2 = ? AND Col3 = ?") for (Data aa : InComingData) { if(null == aa.getCol2()) { ps.setNull(1, java.sql.Types.INTEGER); } else { ps.setInteger(1,aa.getCol2()) } if(null == aa.getCol3()) { ps.setNull(2, java.sql.Types.INTEGER); } else { ps.setInteger(2,aa.getCol3()) } ps.addBatch(); } ps.executeBatch(); connection.commit(); Any help would be appreciated.

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  • Declaring a data type dynamically in C++

    - by Bobby
    I want to be able to do the following: I have an array of strings that contain data types: string DataTypeValues[20] = {"char", "unsigned char", "short", "int"}; Then later, I would like to create a variable of one of the data types at runtime. I won't know at compile time what the correct data type should be. So for example, if at runtime I determined a variable x needed to be of type int: DataTypeValues[3] x = 100; Obviously this won't work, so how could I do something like this?

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  • Question about C Pointers (just learning)

    - by Mike
    I am curious as to why this is an error and what the error message means. Here is some code. int *x[] = {"foo", "bar", "baz"}; int *y[] = {"foo", "bar", "baz"}; x = y; I try to compile and I get this: error: incompatible types when assigning to type ‘char [3]’ from type ‘char *’ Question #1 why is this an error? and Question #2 why are the types different? Thanks for you help.

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  • Reasons for sticking with TEXT, NTEXT and IMAGE instead of (N)VARCHAR(max) and VARBINARY(max)

    - by John Assymptoth
    TEXT, NTEXT and IMAGE have been deprecated a long time ago and will, eventually, be removed from SQL Server. However, they are not going to be discontinued right away, not even in the next version of SQL Server, so it's not convenient for my enterprise to transform thousands of columns right away, even if it is using SQL Server 2012. What arguments can I use to postpone this migration? I know there are some advantages in using the new types. But I'm strictly looking for reasons not to migrate my data that is already functioning pretty well in the old types.

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  • Proper use of use of "cor" function in R

    - by order
    I am interested to know what a proper x (vector matrix or data frame) input looks like. I am currently using the function in two different sorts of matrices. However, I am not sure how R would interpret my data the way I intend. I will explain the types of matrix by example. Type 1 Gene1 Gene2 Gene3 sample1 sample2 Type 2 Sample1 Sample2 Sample3 gene 1 gene 2 gene 3 Are either of these formats valid x parameters? I input both of types of matrices and get some results, but without knowing whether or not this a proper use the function, these are just random numbers. Thank you for your time. I apologize that this isn't more interesting.

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  • Partially parse C++ for a domain-specific language

    - by PierreBdR
    I would like to create a domain specific language as an augmented-C++ language. I will need mostly two types of contructs: Top-level constructs for specialized types or declarations In-code constructs, i.e. to add primitives to make functions calls or idiom easier The language will be used for scientific computing purposes, and will ultimately be translated into plain C++. C++ has been chosen as it seems to offer a good compromise between: ease of use, efficiency and availability of a wide range of libraries. A previous attempt using flex and bison failed due to the complexity of the C++ syntax. The existing parser can still fail on some constructs. So we want to start over, but on better bases. Do you know about similar projects? And if you attempted to do so, what tools would you use? What would be the main pitfalls? Would you have recommendations in term of syntax?

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  • displaying the different uploaded files as thumbnails or any other way

    - by user1529342
    I have written code to upload the files of different types using php, and also i am saving their location information and date in database table. i made a query to display list of files i have uploaded...and resulting output on a html page as follows 1.uploads/clouds.png date and time 2.uploads/resume.pdf dare and time .......so on is there any different any way to display them by their file types as like an operating systems do..... or any better way.... I am curious to know it... Thanks for any help...

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  • SQL finding overlapping of times pass midnight (across 2 days)

    - by janechii
    Hi everyone, I know there are lots of these types of questions, but i didn't see one that was similar enough to my criteria. So i'd like to ask for your help please. The fields i have are just start and end which are of time types. I cannot involve any specific dates in this. If the time ranges don't go pass midnight across day, i'd just compare two tuples as such: end1 > start2 AND start1 < end2 (end points touching are not considered overlapped here.) But when I involve time range that pass (or at) midnight, this obviously doesn't work. For example, given: start | end --------+-------- 06:00PM | 01:00AM 03:00PM | 09:00PM Without involving dates, how can i achieve this, please. My assumption is, if end is less than start, then we're involving 2 days. I'm trying to do this in plain standard SQL, so just a simple and concise logic in the WHERE clause. Thank you everyone!

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  • Differences between extension methods in C#3 & 4

    - by Buh Buh
    I think I remember reading a long time ago that in C#3 extension methods could only be applied to primitive types and interfaces; and that in C#4 they could be used to extend any type. This doesn't seam to match up with what I am seeing now and I am finding it difficult to find this documented. Is there any truth to this or did my memory make it all up? What are the rules relating to which types can be extended? Are there any differences between C# 3 and 4?

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  • How to normalize SVG path data (cross browser)?

    - by Timo
    I have tried to find a way to implement cross browser path normalizer. There IS a native way which is described here and functional example is here, but it works only in newest Opera (but not in IE, FF, Safari, Chrome). The native way uses pathElm.normalizedPathSegList and it converts all relative coordinates to absolute ones and represents all path segment types as a following subset of types: M,L,C,z. I have found only one javascript code and jsfiddled functional example of it, but it works only in IE and FF. Chrome gives "Uncaught Error: INDEX_SIZE_ERR: DOM Exception 1". How this could be fixed to work also in Opera, Safari and Chrome or is there any other way for normalizing SVG paths?

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  • Can't INSERT INTO SELECT into a table with identity column

    - by Eran Goldin
    In SQL server, I'm using a table variable and when done manipulating it I want to insert its values into a real table that has an identity column which is also the PK. The table variable I'm making has two columns; the physical table has four, the first of which is the identity column, an integer IK. The data types for the columns I want to insert are the same as the target columns' data types. INSERT INTO [dbo].[Message] ([Name], [Type]) SELECT DISTINCT [Code],[MessageType] FROM @TempTableVariable END This fails with Cannot insert duplicate key row in object 'dbo.Message' with unique index 'IX_Message_Id'. The duplicate key value is (ApplicationSelection). But when trying to insert just Values (...) it works ok. How do I get it right?

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  • Property hiding and reflection (C#)

    - by tehMick
    Declaring a property in a derived class that matches the name of a property in the base class "hides" it (unless it overrides it with the override keyword). Both the base and derived class properties will be returned by Type.GetProperties() if their types don't match. However, if their types do match, shockingly only the derived class's property is returned. For instance: class A { protected double p; public int P { get { return (int)p; } set { p = value; } } } class B : A { public new int P { get { return (int)p; } set { p = value; } } } class C : B { public new float P { get { return (float)p; } set { p = value; } } } Calling typeof(C).GetProperties() will only return B.P and C.P. Is it possible to call GetProperties() in a way that returns all three? There is almost certainly a way to do it by traversing the inheritance hierarchy, but is there a cleaner solution?

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  • find: missing argument to -exec

    - by Abs
    Hello all, I was helped out today with a command, but it doesn't seem to be working. This is the command: find /home/me/download/ -type f -name "*.rm" -exec ffmpeg -i {} -sameq {}.mp3 && rm {}\; The shell returns find: missing argument to `-exec' What I am basically trying to do is go through a directory recursively (if it has other directories) and run the ffmpeg command on the .rm file types and convert them to .mp3 file types. Once this is done, remove the .rm file that has just been converted. I appreciate any help on this.

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