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• MySQL LEFT JOIN, GROUP BY and ORDER BY not working as required

  - by Simon

  I have a table 'products' => ('product_id', 'name', 'description') and a table 'product_price' => ('product_price_id', 'product_id', 'price', 'date_updated') I want to perform a query something like SELECT `p`.*, `pp`.`price` FROM `products` `p` LEFT JOIN `product_price` `pp` ON `pp`.`product_id` = `p`.`product_id` GROUP BY `p`.`product_id` ORDER BY `pp`.`date_updated` DESC As you can probably guess the price changes often and I need to pull out the latest one. The trouble is I cannot work out how to order the LEFT JOINed table. I tried using some of the GROUP BY functions like MAX() but that would only pull out the column not the row. Thanks.

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• misleading plot issue in mathematica

  - by Qiang Li

  I want to study some "strange" functions by plotting them out in mathematica. One example is the following: mod2[x_] := Which[Mod[x, 2] >= 1, -2 + Mod[x, 2], True, Mod[x, 2]]; f[x_] := Which[-1 <= x <= 1, Abs[x], True, Abs[mod2[x]]]; fn[x_, n_] := Sum[(3/4)^i*f[4^n*x], {i, 0, n}] Plot[{fn[x, 0], fn[x, 1], fn[x, 2], fn[x, 5]}, {x, -2, 2}] However, the plot I got from mma is misleading, in the sense that the maxima and minima of fn[x, 5] should be on the same two levels. But due to high oscillation of the function, and the fact that clearly mma only takes limited number of points to draw the function, you see the plot exhibit strange behavior. Is there any option in plot to remedy for this? Many thanks.

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• Can I save my app's state at close time in iPhone OS?

  - by Steve

  I have an app that functions much like an ebook. I have a bunch of textual information in various languages that is accessible through a number of drill down methods. When a user wants to get into where they were reading last, they currently have to navigate through the section and chapter menus to get back to where they were. An ideal solution for this would be to setup a bookmark system, which I am considering. But if I remember correctly, when iPhone OS 4 was announced, they seemed to make a big deal of the added ability to save the state of an app. Does that mean that someone using my reader app would be able to just exit right out, do whatever, and then when they came back in, it would be the reading screen just as they left it? I don't know much about how to setup a bookmarking system, I suppose it would be worth investigating, but I would probably want to just hold off for iPhone OS 4 if that is indeed what it will be capable of doing. Any thoughts or insights would be appreciated!!

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• Is there an equivalent to C++'s "friend class" in Java?

  - by Ricket

  In C++ there is a concept of a "friend", which has access to a class's private variables and functions. So if you have: class Foo { friend class Bar; private: int x; } then any instance of the class Bar can modify any Foo instance's x member, despite it being private, because Bar is a friend of Foo. Now I have a situation in Java where this functionality would come in handy. There are three classes: Database, Modifier, Viewer. The Database is just a collection of variables (like a struct). Modifier should be "friends" with Database; that is, it should be able to read and write its variables directly. But Viewer should only be able to read Database's variables. How is this best implemented? Is there a good way to enforce Viewer's read-only access of Database?

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• Objective-C : Changing "self" value inside self

  - by Oliver

  Hello, I have a category on NSDate, and I want to implement some functions to manipulate the date, like : NSDate *thedate = [NSDate date]; [thedate setToMidnight]; so I have a function in NSDate like : -(void)setToMidnight { some code with calendars and comps self = theNewDate; } This works inside the function, but outside this member function, thedate has not changed. I understand this malfunction because I've been told that self is just a local variable created inside the member function. So, how can I make this work ? Of course, I could have written : thedate = [thedate dateAsMidnightDate] or thedate = [NSDate dateAtMidnightFromDate:thedate] but I feel it has more sense inside the instance class, as I don't want to change the date but just adjust some values of the previously created one. Can you help me to achieve this ?

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• advanced search with mysql

  - by Arsenal

  I'm creating a search function for my website where the user can put in anything he likes in a textfield. It get's matched against anything (name, title, job, car brand, ... you name it) I initially wrote the query with an INNER JOIN on every table that needed to be searched. SELECT column1, column2, ... FROM person INNER JOIN person_car ON ... INNER JOIN car ... This ended up in a query with 6 or 8 INNER JOINs, and a whole lot WHERE ... LIKE '%searchvalue%' Now this query seems to cause a time'out in MySql, and I even got a warning from my hosting provider that the queries just taking up too many resources. Now obviously I'm doing this very wrong, but I was wondering how the correct approach to these kind of search functions is. Thanks!

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• Remove duplicates in entries, scala way

  - by andersbohn

  I have a list of entries stating a production value in a given interval. Entries stating the exact same value at a later time adds no information and can safely be left out. case class Entry(minute:Int, production:Double) val entries = List(Entry(0, 100.0), Entry(5, 100.0), Entry(10, 100.0), Entry(20, 120.0), Entry(30, 100.0), Entry(180, 0.0)) Experimenting with the scala 2.8 collection functions, so far I have this working implementation: entries.foldRight(List[Entry]()) { (entry, list) => list match { case head :: tail if (entry.production == head.production) => entry :: tail case head :: tail => entry :: list case List() => entry :: List() } } res0: List[Entry] = List(Entry(0,100.0), Entry(20,120.0), Entry(30,100.0), Entry(180,0.0)) Any comments? Am I missing out on some scala magic?

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• How to check for C++ copy ellision

  - by Steve

  I ran across this article on copy ellision in C++ and I've seen comments about it in the boost library. This is appealing, as I prefer my functions to look like verylargereturntype DoSomething(...) rather than void DoSomething(..., verylargereturntype& retval) So, I have two questions about this Google has virtually no documentation on this at all, how real is this? How can I check that this optimization is actually occuring? I assume it involves looking at the assembly, but lets just say that isn't my strong suit. If anyone can give a very basic example as to what successful ellision looks like, that would be very useful I won't be using copy ellision just to prettify things, but if I can be guaranteed that it works, it sounds pretty useful.

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• Return from parent sub in Perl

  - by JS Bangs

  I want to write a subroutine which causes the caller to return under certain conditions. This is meant to be used as a shortcut for validating input to a function. What I have so far is: sub needs($$) { my ($condition, $message) = @_; if (not $condition) { print "$message\n"; # would like to return from the *parent* here } return $condition; } sub run_find { my $arg = shift @_; needs $arg, "arg required" or return; needs exists $lang{$arg}, "No such language: $arg" or return; # etc. } The advantage of returning from the caller in needs would then be to avoid having to write the repetitive or return inside run_find and similar functions.

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• Which PHP calendar will suit my needs? Or build my own?

  - by John

  There are so many web based calendars out there that I'm not sure which will best suit my purposes. I want to create an events calendar, which I suppose looks and functions in much the same way as google calendar. But users shouldn't need to sign up for a gmail account or a google account. Users of my social network website should be able to create events in the calendar and share it with other friends in their "friend network". In month, year or day views, you can mouse hover events to see a bubble dialog that lists events in detail. People need to pay a monthly fee to use my website (not sure if this prevents me from using google apps). So is something like Google Calendar the way to go? Or are there other php/javascript calendars out there that already meet my needs? Or will it just save me more time to build my own?

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• Is there anything wrong with a class with all static methods?

  - by MatthewMartin

  I'm doing code review and came across a class that uses all static methods. The entrance method takes several arguments and then starts calling the other static methods passing along all or some of the arguments the entrance method received. It isn't like a Math class with largely unrelated utility functions. In my own normal programming, I rarely write methods where Resharper pops and says "this could be a static method", when I do, they tend to be mindless utility methods. Is there anything wrong with this pattern? Is this just a matter of personal choice if the state of a class is held in fields and properties or passed around amongst static methods using arguments?

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• Ruby On Rails CMS Framework

  - by stel

  Hi! I want to create a framework fo rails application. It will be a rails application but packed into gem (like a Radiant CMS). It must work like this: gem install cmsframework and then: cmsframework the_app After that we have a sceleton of rails app without any controllers etc.. - all controllers loaded from cmsframework gem. If I want to rewrite some files (for example public/styles.css) I must simply create it in my app (the_app). If I want new functions in my app I can create a plugin. But the main functionalities must be loaded from cmsframework gem. What is the best way to implement this?

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• Porting Windows C++ to Standard (Linux) C++ - WSAGetLastError()

  - by Donal Rafferty

  I am currently porting some Windows mobile C++ code to standard C++. So I am trying to find alternatives for windows specific functions. I have had very little luck in finding a standard C++ function that can help me replace the WSAGetLastError() windows specific function. WSAGetLastError() returns error numbers for errors that occur with sockets in windows. So I was wondering if anyone was aware of a way to replace this function in standard c++? A way to get different error numbers for different outcomes of connecting/dissconection a socket would be sufficent.

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• Updating variables in XSL

  - by Stroboskop

  Is there any way in XSL to update a global variable? I want to check what elements i already transformed and act accordingly. That would require me to somehow add the names of the elements to some sort of list and update it each time a new element is transformed. But since xsl:variable isn't "variable" in the sense one would expect, i have no way of adding anything to it once it has been defined. I have multiple included data files, so using xsl functions that only know the current set of nodes will not help.

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• matrix = *((fxMatrix*)&d3dMatrix); //Evil?

  - by Xilliah

  I've been using matrix = *((fxMatrix*)&d3dMatrix); for quite a while. It worked fine until my screen turned black and received a bucket of frustration on my desk. fxMatrix contains 4 fxVectors. fxVector used to be 16 bytes, but now it was suddenly 20. This was because it inherited fxStreamable, which added the vTable. So one solution is of course just to not inherit fxStreamable, and leave a comment saying that it must always be 16 bytes and never more. Another solution would be to make conversion functions, and copy the matrix completely. This makes it more secure, but has an impact on the performance. I suppose this is the best idea. Another solution is to not convert at all, and stick to D3DXMATRIX, but this makes the engine inconsistent and I personally really dislike this idea. What is your opinion?

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• Customer provider Password Reset client.

  - by ProfK

  I'm looking for guidence on writing a custom password reset UI, but it must fit the Provider 'Pattern', or degrade silently to built-in defaults. E.g. my Reset Control must collect extra information, and perform differently to the standard Password Recovery Control. It must close as possible use the standard MembershipProvider interface for standard functions, and only use an extended interface for the non-standard stuff. I'd like some reading on issues such as, what must I ask the Membership Provider for, and what must I do myself. What must I tell the provider (service?) about what I do? Etc.

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• Is there any free, open source php CMS\framework for described case?

  - by Ole Jak

  I want that cms\framework to create me tables like "Users" "Cameras" and so on and declare classes and simple default methods for them (like paged sql relults and so on). I mean I say to it: I want Users to have ID, SpecialNumber and Name Flilds. and I want to get from it class for table generation (to call it once) and class containing methods such as Search by ID, SpecialNumber and Name, Create User, Delit User and so on functions. Is there any framework/cms like this for working with CODE not ui's and so on... so to say PHP generator or something... The result should be as that framework free as possible. So Is there any free, open source php CMS\framework for described case?

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• portable way to deal with 64/32 bit time_t

  - by MK

  I have some code which is built both on Windows and Linux. Linux at this point is always 32bit but Windows is 32 and 64bit. Windows wants to have time_t be 64 bit and Linux still has it as 32 bit. I'm fine with that, except in some places time_t values are converted to strings. So when time_T is 32 bit it should be done with %d and when it is 64bit with %lld... what is the smart way to do this? Also: any ideas how I may find all places where time_t's are passed to printf-style functions to address this issue?

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• MySql returning multiple rows from stored procedure / function

  - by pistacchio

  Hi, I need to make a stored procedure or function that returns a set of rows. I've noted that in a stored procedure i can SELECT * FROM table with success. If i fetch rows in a loop and SELECT something, something_other FROM table once per loop execution, I only get one single result. What I need to do is looping, doing some calculations and returning a rowset. What's the best way to do this? A temporary table? Stored functions? Any help appreciated.

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• C++ Basic Class Layout

  - by Spencer

  Learning C++ and see the class laid out like this: class CRectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; void CRectangle::set_values (int a, int b) { x = a; y = b; } I know Java and methods(functions) in Java are written within the class. The class looks like a Java interface. I know I can write the class like this: class CRectangle { int x, y; public: void set_values (int a, int b) { x = a; y = b; }; int area () {return (x*y);} }; But is there a difference or standard?

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• Handling the distinction between undefined- and null-parameters in JavaScript

  - by Jakob

  I know very well that null and undefined are distinct in JavaScript. However, I can't seem to decide whether or not use that fact when my own functions are passed one of those as its argument. Or, expressed in a different way, should myFoo(undefined) return the same thing as myFoo(null) or is everything fine if it doesn't? Or, in yet another case, since myBar(1, 2, 3) is the same thing as myBar(1, 2, 3, undefined, undefined), should myBar(1, 2, 3, null, null) return the same thing as myBar(1, 2, 3)? I feel that there's potential for confusion in both cases and that a library should probably follow a convention when handling null/undefined. I'm not really asking for personal opinions (so please express those as comments rather than answers). I'm asking if anyone knows if there is a best practice that one should stick to when it comes to handling this distinction. References to external sources are very welcome!

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• WinXP Parallels Guest with OS X host -- communication between the two?

  - by Justin

  The setup: Windows XP guest OS running inside Parallels 5 on a OS X 10.6.2 host. I have a win32 application that runs in windows that communicates with other programs by sending out keystrokes to the program in focus. I can run this software inside parallels just fine, but I need a way for it to communicate (via keystrokes) with native OS X applications. For instance, the windows software sends out a continuous stream of a's and w's, based on the program input from an external source. On the other side, I have a Mac version of VLC media player with hotkeys set up for a and w for the two functions I would like to manipulate from the windows software. How can I set up a link between the guest and host OS's with Parallels that lets a windows program send keystrokes to a mac program?

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• XCode iPhone OS Deployment Target Tool

  - by Trah Divad

  Problem I'm currently stuck trying to figure out what "iPhone OS Deployment Target" setting to use. I do not want to write conditional code right now, so I'd like the lowest version that runs my application fine. At first I thought it would be 2.0 as I wasn't using any 3.0 features, but then i realized that AVAudioRecorder is a 3.0 API. I don't want to be manually checking EVERY function I use in the documentation. Question Is there a tool that will check the OS availability of each functions you call in your code to figure out what the Deployment Target should be? That tool could be a good old compiler, but the latest version of the iPhone SDK does not come with the PRE-3.0 SDKs.

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• Separate one-off code paths

  - by DeadMG

  I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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• Design pattern: Polymorphism for list of objects

  - by ziang

  Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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