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• Advanced LINQ Update Statement

  - by user1902490

  I have a data base with Price_old like: Date --- Hour --- Price _____________________________ Jan 1 --- 1 --- $3.0 Jan 1 --- 2 --- $3.1 Jan 1 --- 3 --- $3.3 Jan 1 --- 4 --- $3.15 Jan 2 --- 1 --- $2.95 Jan 2 --- 2 --- $3.2 Jan 2 --- 3 --- $3.05 What I then have is a spreadsheet, with the same structure, that I will be reading into a datatable, I'll call the new datatable Price_New, note that price new may not have all the same date/hours as Price_Old So, I end up with 2 datatables, Price_Old, and Price_New, and what I need to do is update Price_old with the new prices in Price_New, and then commit those new prices to the Database. I am kinda new to LINQ (about 30 mins of experience) and would really appreciate if someone could give me a pointer or two on whether or not this is doing in LINQ and what the best method would be. Thanks

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• Socket programming question

  - by dfddf

  I am given the following declaration: char inbuff[500], *ptr; int n, bufferlen; Write a program segement to receive a message having 500 bits from the TCP socket sock and store this message in inbuff. My answer is: n = recv( sock, inbuff, strlen( inbuff ), 0 ); However, I am not sure why *ptr is given in the declaration. So, I would like ask, what is the purpose of the pointer in this question?? Or my program segement is wrong? Thank you for all of yours help first!

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• use callback function to report stack backtrace

  - by user353394

  Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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• correct way to store an exception in a variable

  - by Evan Teran

  I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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• can't click on input element behind div element

  - by Preston

  On my site: http://alsite.com.br/solalev/ I have some elements on the bottom of page that I can't click through. Above the elements is a div called push.. I use this div to make the footer always stay on the bottom of my page even when the content is smaller... (I dont know if I do this right.. but it has worked).. So.. on Chrome and Firefox I can't click.. but on IE this works.... I use this: .push{ pointer-events: none; } but nothing happens...

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• which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project?

  - by Greg

  Hi, Which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project? (e.g. sql server express, sql server ce, full version etc). That is, I'm running on a VMWare fusion instance on my MacBook, and just want something to develop against for a C# VS2010 project. I'm planning on having a simple database (not many tables) but will use Entity Framework. I haven't used SQL Server before so a quick pointer re what is the best database admin interface/app to use for the version you recommend (e.g. to create database, tables etc).

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• A question on vectors, pointers and iterators

  - by xbonez

  Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated. Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions: what type is p? what type is *p? what code provides the address of the actual Thingie? what code provides the actual Thingie?

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• jQuery li:has(ul) selector issue

  - by sushil bharwani

  I was creating a tree using UL LI list and jQuery. I used a jQuery Selector jQuery(li:has(ul)) to find all the list nodes having childs and then added a click event to it. jQuery(li:has(ul)).click(function(event) { jQuery(this).children.toggle(); jQuery(this).css("cursor","hand"); }); This works for me except i dont understand why i get a cursor hand and click event triggering even when i take mouse pointer to childs of my selected li <li> Parent // it works here that is fine <ul> <li> child1 // it works here i dont understand need explanation </li> <li> child2 // it works here i dont understand need explanation </li> </ul> </li>

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• Determining a location's side of the road position with MapKit

  - by idStar

  Is there a way to use MapKit in iOS7 to not only get geocoding for an address, but determine what side of the road it is on? I'm not trying to build a full function navigation app, but similar to navigation apps that tell you things like "Your destination is in 100 feet on the right", I'd like to be able to obtain this information. Does MapKit give one a way to do this? Do I need to adopt routing privileges to access such, or is this just not available in the SDK period? If not available in the iOS7 SDK, knowing what options exist as services, would be a helpful pointer.

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• STL map containing references does not compile

  - by MTsoul

  The following: std::map<int, ClassA &> test; gives: error C2101: '&' on constant While the following std::map<ClassA &, int> test; gives error C2528: '_First' : pointer to reference is illegal The latter seems like map cannot contain a reference for the key value, since it needs to instantiate the class sometimes and a reference cannot be instantiated without an object. But why does the first case not work?

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• How can I highlight the line of text that is closest to the mouse?

  - by Aaron Digulla

  I have a long text and I'd like to offer the user a reading help: The current line should be highlighted. To make it easier, I'll just use the Y coordinate of the mouse (this way, the mouse pointer isn't going to get in the way). I have a big DIV with the id content which fills the whole width and a small DIV with the class content for the text (see here for an example). I'm using jQuery 1.4. How can I highlight the line of text that is closest to the current mouse position?

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• How do I draw an arrow on a histogram drawn using ggplot2?

  - by jon

  Here is dataset: set.seed(123) myd <- data.frame (class = rep(1:4, each = 100), yvar = rnorm(400, 50,30)) require(ggplot2) m <- ggplot(myd, aes(x = yvar)) p <- m + geom_histogram(colour = "grey40", fill = "grey40", binwidth = 10) + facet_wrap(~class) + theme_bw( ) p + opts(panel.margin=unit(0 ,"lines")) I want to add labels to bars which each subject class fall into and produce something like the post-powerpoint processed graph. Is there way to do this within R ? ...... Edit: we can think of different pointer such as dot or error bar, if arrow is not impossible Let's say the following is subjects to be labelled: class name yvar 2 subject4 104.0 3 subject3 8.5 3 subject1 80.0 4 subject2 40.0 4 subject1 115.0 classd <- data.frame (class = c(2,3,3,4,4), name = c ("subject4", "subject3", "subject1", "subject2", "subject1"), yvar = c(104.0, 8.5,80.0,40.0, 115.0))

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• How do I modify the -encoding argument to javac in the Android Ant build system

  - by Paul Butcher

  Apologies if this is a stupid question - I'm an Android and Ant newbie. I have utf8 encoded source files that I need to compile with the Android Ant build system. By default, the encoding is set to ascii. I'd be very grateful for a pointer to whatever I need to do to let the build system know that my files are utf8. Incidentally, it works fine if I build in Eclipse, but I need to build from the command line. Thanks!

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• When to pass by value?

  - by Dervin Thunk

  Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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• How to sanely read and dump structs to disk when some fields are pointers?

  - by bp

  Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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• multiple C++ deletion of a memory pointed by multiple objects

  - by elgcom

  Another c++ pointer deletion question is in the following example: class Foo { public: int *p; ~Foo() { delete p; p = NULL; } }; Foo *f1 = new Foo(); Foo *f2 = new Foo(); f1->p = new int(1); f2->p = f1->p; delete f2; // ok delete f1; // no error? Why I did not get error when calling "delete f1"? didn't I delete the same address (*p) twice? If I directly delete the pointers in the last 2 lines of code, I will get error. delete f2->p; // ok delete f1->p; // error!! *** glibc detected *** double free or corruption (fasttop) ***

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• how to open many files simultaneously for reading in c

  - by monkeyking

  I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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• JQuery Autocomplete - Stop mouseover+Return submitting data

  - by ILT

  I'm using JQuery Autocomplete (bassistance) and have run into a problem. If the mouse rolls over one of the autocomplete suggestions and the user hits the return key (rather than clicking to make selection), the form is submitted and goes to whatever link was rolled over at the time. This is a problem as people click in the textbox, and when typing their search, leave the pointer where the autocomplete popup appears. So when they hit enter, it doesn't do the search for whatever they typed in the box but whatever was highlighted in the autocomplete suggestions. Is there a way to stop this? Using Google as the functionality I'm after... So just to clarify - I want selections via mouse and keyboard to go to the same place, but if the UP or DOWN arrow has not been pressed (user not selected an autocomplete option via the keyword), dont go to the URL specified in the autosuggest - instead submit the form (traditional method without JQuery) based on what has been typed in the textbox. I hope I'm explaining this clearly? :S

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• Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

  - by Will

  I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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• How to define a static array without a contant size in a constructor of a class? (C++)

  - by Keand64

  I have a class defined as: class Obj { public: int width, height; Obj(int w, int h); } and I need it to contain a static array like so: int presc[width][height]; however, I cannot define within the class, so it it possible to create a pointer to a 2D array (and, out of curiosity, 3, 4, and 5D arrays), have that as a member of the class, and intitalize it in the constructor like: int ar[5][6]; Obj o(5, 6, &ar); If that isn't possible, is there any way to get a static array without a contant size in a class, or am I going to have to use a dynamic array? (Something I don't want to do because I don't plan on ever changing the size of the array after it's created.)

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• How to name variables wich are structs

  - by evilpie

  Hello, i often work on private projects using the WinApi, and as you might know, it has thousands of named and typedefed structs like MEMORY_BASIC_INFORMATION. I will stick to this one in my question, what still is preferred, or better when you want to name a variable of this type. Is there some kind of style guide for this case? For example if i need that variable for the VirtualQueryEx function. Some ideas: MEMORY_BASIC_INFORMATION memoryBasicInformation; MEMORY_BASIC_INFORMATION memory_basic_information; Just use the name of the struct non captialized and with or without the underlines. MEMORY_BASIC_INFORMATION basicInformation; MEMORY_BASIC_INFORMATION information; Short form? MEMORY_BASIC_INFORMATION mbi; I often see this style, using the abbreviation of the struct name. MEMORY_BASIC_INFORMATION buffer; VirtualQueryEx defines the third parameter lpBuffer (where you pass the pointer to the struct), so using this name might be an idea, too. Cheers

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• WPF: How to efficiently update an Image 30 times per second

  - by John

  Hello, I'm writing a WPF application that uses a component, and this component returns a pointer (IntPtr) to pixels of a bitmap (stride * height). I know in advance that the bitmap is a 24bits rgb, its width and height. Updating the Image control with these bitmaps makes up a video to the user, but I'm not sure what's the most efficient way to do that, most of the time the CPU usage goes to 75%+ and memory changing from 40mb to 500mb and the nI think GC starts to work and then it drops again to 40mm. The app starts to not be responsive. What shoud I do? thanks!

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• How to vertically align images in <td>

  - by Ricky

  I got a <td> where two images () reside shown as follows. One is much higher than the other. How do I let the shorter one align to the top of <td />? <td style="padding-left: 0px; cursor: pointer; vertical-align: top;"> <img width="85px" src=".../xyz.png"/> <img src=".../icon_live.gif" /> // shorter one </td>

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• OpenGL texture not showing up on some computers, problem with auxDIBImageLoad?

  - by CptanPanic

  I have a simple openGL GUI that has uses a bmp as a texture. The problem is on some computers the texture doesn't show up. But on ones with newer OpenGL drivers it works. How can I make it more compatible. I think the problem may be with auxDIBImageLoad. When I inspect the result, I see the x,y correct, but the data pointer points to memory bank with all zeros. What could be wrong?

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• Real thing about "->" and "."

  - by fsdfa

  I always wanted to know what is the real thing difference of how the compiler see a pointer to a struct (in C suppose) and a struct itself. struct person p; struct person *pp; pp->age, I always imagine that the compiler does: "value of pp + offset of atribute "age" in the struct". But what it does with person.p? It would be almost the same. For me "the programmer", p is not a memory address, its like "the structure itself", but of course this is not how the compiler deal with it. My guess is it's more of a syntactic thing, and the compiler always does (&p)->age. I'm correct?

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