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• Is there a name for the technique of using base-2 numbers to encode a list of unique options?

  - by Lunatik

  Apologies for the rather vague nature of this question, I've never been taught programming and Google is rather useless to a self-help guy like me in this case as the key words are pretty ambiguous. I am writing a couple of functions that encode and decode a list of options into a Long so they can easily be passed around the application, you know this kind of thing: 1 - Apple 2 - Orange 4 - Banana 8 - Plum etc. In this case the number 11 would represent Apple, Orange & Plum. I've got it working but I see this used all the time so assume there is a common name for the technique, and no doubt all sorts of best practice and clever algorithms that are at the moment just out of my reach.

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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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• How to create a string array in matlab?

  - by aduric

  I would like to pass a vector of strings from C++ to matlab. I have tried using the functions available such as mxCreateCharMatrixFromStrings but it doesn't give me the correct behavior. So, I have something like this: void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { vector<string> stringVector; stringVector.push_back("string 1"); stringVector.push_back("string 2"); //etc... The problem is how do I get this vector to the matlab environment? plhs[0] = ??? My goal is to be able to run: >> [strings] = MyFunc(...) >> strings(1) = 'string 1'

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• Must a Language that Implements Monads be Statically Typed?

  - by Morgan Cheng

  I am learning functional programming style. From this link http://channel9.msdn.com/shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads/, Brian Beckman gave a brilliant introduction about Monad. He mentioned that Monad is about composition of functions so as to address complexity. A Monad includes a unit function that transfers type T to an amplified type M(T); and a Bind function that, given function from T to M(U), transforms type M(T) to another type M(U). (U can be T, but is not necessarily). In my understanding, the language implementing monad should be type-checked statically. Otherwise, type errors cannot be found during compilation and "Complexity" is not controlled. Is my understanding correct?

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• Setting the Cursor Position in a Win32 Console Application

  - by Jim Fell

  How can I set the cursor position in a Win32 Console application? Preferably, I would like to avoid making a handle and using the Windows Console Functions. (I spent all morning running down that dark alley; it creates more problems than it solves.) I seem to recall doing this relatively simply when I was in college using stdio, but I can't find any examples of how to do it now. Any thoughts or suggestions would be greatly appreciated. Thanks.

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• AbsoluteTime with numeric argument behaves strangely.

  - by dreeves

  This is strange: DateList@AbsoluteTime[596523] returns {2078, 7, 2, 2, 42, 9.7849} But DateList@AbsoluteTime[596524] returns {1942, 5, 26, 20, 28, 39.5596} The question: What's going on? Note that AbsoluteTime with a numeric argument is undocumented. (I think I now know what it's doing but figured this is useful to have as a StackOverflow question for future reference; and I'm curious if there's some reason for that magic 596523 number.) PS: I encountered this when writing these utility functions for converting to and from unix time in Mathematica: (* Using Unix time (an integer) instead of Mathematica's AbsoluteTime... *) tm[x___] := AbsoluteTime[x] (* tm is an alias for AbsoluteTime. *) uepoch = tm[{1970}, TimeZone->0]; (* unixtm works analogously to tm. *) unixtm[x___] := Round[tm[x]-uepoch] (* tm & unixtm convert between unix & *) unixtm[x_?NumericQ] := Round[x-uepoch] (* mma epoch time when given numeric *) tm[t_?NumericQ] := t+uepoch (* args. Ie, they're inverses. *)

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• Setting creation or change timestamps

  - by Thanatos

  Using utimes, futimes, futimens, etc., it is possible to set the access and modification timestamps on a file. Is there a function to set change timestamps? (I understand the cyclic nature of wanting to change the change timestamp, but think archiving software - it would be nice to restore a file exactly as it was.) Are there any functions at all for creation timestamps? (I realize that ext2 does not support this, but I was wondering if Linux did, for those filesystems that do support it.) If it's not possible, what is the reasoning behind it not being so?

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• Recursive compilation using gcc

  - by curiousexplorer

  I am using the gcc compiler. My project source tree looks like somewhat like this test$~: tree . . |-- folder | |-- hello.cpp | `-- hello.h `-- main.cpp 1 directory, 3 files test$~: The file main.cpp contains the main() function and all the functions invoked by main.cpp lie in the directory named folder So far in all my little projects I never had to put some source code under a sub-directory. What I am looking for, in short, is some gcc command for recursive compilation in sub-directories and their subdirectories and so on... This command should be invoked from the home directory of the code project.

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• Template type deduction with a non-copyable class

  - by Evan Teran

  Suppose I have an autolocker class which looks something like this: template <T> class autolocker { public: autolocker(T *l) : lock(l) { lock->lock(); } ~autolocker() { lock->unlock(); } private: autolocker(const autolocker&); autolocker& operator=(const autolocker&); private: T *lock; } Obviously the goal is to be able to use this autolocker with anything that has a lock/unlock method without resorting to virtual functions. Currently, it's simple enough to use like this: autolocker<some_lock_t> lock(&my_lock); // my_lock is of type "some_lock_t" but it is illegal to do: autolocker lock(&my_lock); // this would be ideal Is there anyway to get template type deduction to play nice with this (keep in my autolocker is non-copyable). Or is it just easiest to just specify the type?

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• Group MySQL Data into Arbitrarily Sized Time Buckets

  - by Eric J.

  How do I count the number of records in a MySQL table based on a timestamp column per unit of time where the unit of time is arbitrary? Specifically, I want to count how many record's timestamps fell into 15 minute buckets during a given interval. I understand how to do this in buckets of 1 second, 1 minute, 1 hour, 1 day etc. using MySQL date functions, e.g. SELECT YEAR(datefield) Y, MONTH(datefield) M, DAY(datefield) D, COUNT(*) Cnt FROM mytable GROUP BY YEAR(datefield), MONTH(datefield), DAY(datefield) but how can I group by 15 minute buckets?

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• Why use event listeners over function calls?

  - by Organiccat

  I've been studying event listeners lately and I think I've finally gotten them down. Basically, they are functions that are called on another object's method. My question is, why create an event listener when calling the function will work just fine? Example, I want to call player.display_health(), and when this is fired, the method player.get_health() should be fired and stored so that display_health() has access to it. Why should I use an event listener over simply calling the function? Even if display_health() were in another object, this still doesn't appear to be a problem to me. If you have another example that fits the usage better, please let me know. Perhaps particular languages don't benefit from it as much? (Javascript, PHP, ASP?)

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• Getters and Setters: Code smell, Necessary Evil, or Can't Live Without Them [closed]

  - by Avery Payne

  Possible Duplicate: Allen Holub wrote “You should never use get/set functions”, is he correct? Is there a good, no, a very good reason, to go through all the trouble of using getters and setters for object-oriented languages? What's wrong with just using a direct reference to a property or method? Is there some kind of "semantical coverup" that people don't want to talk about in polite company? Was I just too tired and fell asleep when someone walked out and said "Thou Shalt Write Copious Amounts of Code to Obtain Getters and Setters"? Follow-up after a year: It seems to be a common occurrence with Java, less so with Python. I'm beginning to wonder if this is more of a cultural phenomena (related to the limitations of the language) rather than "sage advice". The -1 question score is complete for-the-lulz as far as I am concerned. It's interesting that there are specific questions that are downvoted, not because they are "bad questions", but rather, because they hit someone's raw nerve.

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• Facebook javascript in address bar, possible to replicate?

  - by DoMx

  This is my first experience with stackoverflow and I'm afraid my question asks of a lot for a first. I was looking at this thread: http://stackoverflow.com/questions/2634159/javascrypt-in-the-adress-bar-is-this-malicious and as you will see SLaks has very kindly deobfuscated the javascript and left us with what appears as the Javascript behind the automatic facebook invite code. As I'm fairly new to javascript, I was wondering, what other components were needed to get this code to work? You of course have the functions there and they are called by the obfuscated javascript but how exactly? Would it be possible to replicate this on a page of my own using the information available or is there more to this script I am missing? I am willing to financially assist somebody who could compile a solution for me. Thank you in advance.

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• Help using the Office Interop for Word and Outlook 2007 in VB.NET

  - by vhorsen

  I need to start utilizing the interop in my programs to automate several functions in Word and Outlook and I was checking if anyone knew a good place to start. My ultimate goal is for my program to kick off a mail merge, create several different files and save them accordingly, then e-mail the different files to different people based upon who needs what. So any help on learning how to use the interop properly would be greatly appreciated. I am currently using Visual Studio 2008 and Office 2007 and use vb.net to write my programs. Thank you in advance.

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• How can I upload a file to a Sharepoint Document Library using Silverlight and client web-services?

  - by pclem12

  Most of the solutions I've come across for Sharepoint doc library uploads use the HTTP "PUT" method, but I'm having trouble finding a way to do this in Silverlight because it has restrictions on the HTTP Methods. I visited this http://msdn.microsoft.com/en-us/library/dd920295(VS.95).aspx to see how to allow PUT in my code, but I can't find how that helps you use an HTTP "PUT". I am using client web-services, so that limits some of the Sharepoint functions available. That leaves me with these questions: Can I do an http PUT in Silverlight? If I can't or there is another better way to upload a file, what is it? Thanks

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• How to join table to itself and select max values in SQL

  - by Jakub Konop

  I have a contracts table: contractId date price partId 1 20120121 10 1 2 20110130 9 1 3 20130101 15 2 4 20110101 20 2 The contract with greatest date being the active contract (don't blame me, I blame infor for creating xpps) I need to create query to see only active contracts (one contract per part, the contract with highest date). So the result of the query should be like this: contractId date price partId 1 20120121 10 1 3 20130101 15 2 I am out of ideas here, I tried self joining the table, I tried aggregation functions, but I can't figure it out. If anyone would have any idea, please share them with me..

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• Should I use C++0x Features Now?

  - by svu2g

  With the official release of VS 2010, is it safe for me to start using the partially-implemented C++0x feature set in my new code? The features that are of interest to me right now are both implemented by VC++ 2010 and recent versions of GCC. These are the only two that I have to support. In terms of the "safety" mentioned in the first sentence: can I start using these features (e.g., lambda functions) and still be guaranteed that my code will compile in 10 years on a compiler that properly conforms to C++0x when it is officially released? I guess I'm asking if there is any chance that VC++ 2010 or GCC will end up like VC++ 6; it was released before the language was officially standardized and consequently allowed grossly ill-formed code to compile. After all, Microsoft does say that "10 is the new 6". ;)

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• Is there a language designed for code golf?

  - by J S

  I am not really a fan of code golf, but I have to wonder, is there an esoteric language designed for it? I mean a language with following properties: Common programs may be expressed in very short amount of characters It uses ASCII character set effectively (for example, common operators are not identifiers, so they don't have to be separated by whitespace, character usage is distributed more or less evenly because we cannot use Huffman coding and so on) Except the terse syntax, it should have very expressible and clean semantics (like, let's say, Python or Scheme); it shouldn't be difficult to program in It doesn't need features for large scale programs, such as OOP, but it definitely should allow custom functions and data structures It should have a large standard library, identifiers in this library should be as short as possible Maybe it should be called CG? Languages that can be a source of inspiration are Forth, APL and Joy.

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• Generating random numbers in C

  - by moonstruckhorrors

  While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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• Switching Javascript Function states

  - by webzide

  Dear experts, I would like to implement a API of Javascript that sort of resemble a light switch. For instance, there are two buttons on the actual HTML page act as the UI. Both of the buttons have event handlers that invokes a different function. Each function have codes that act like a state, for instance. button1.onclick=function (){ $("div").click( //code effects 2 ) } button2.onclick=function (){ $("div").click( //Code effects 2 ) } I the code works fine on the surface but the 2 state functions overlap. the effects is going to take place for the rest of the way until the next reload of the document. Basically what I want to achieve is that when 1 button is clicked, it will switch "OFF" the state of function invoked by the other button and vice versa. Thus, the effects achieved are unique are not overlapped. Is there anyway to achieve this or could any experts point me to the right direction. Thanks in advance.

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• Webservice and ORM Framework?

  - by Sebastian

  Does anybody know a good web framework that includes an ORM mapper and allows straight forward implementation of web services? I'm looking for a framework written in PHP or C++. I'm looking for the following features (not all of them required, some will do nicely) data definition in one place used by database and web service WSDL generation XML output/JSON output boilerplate code generation So what I would like is a framework that let's me specify the objects, the web service functions on those objects and then generate everything that is required leaving me to fill the business logic (connecting the database to the web service). Anything like that out there? Background information for why I need this: I'm looking into creating a web project: the client is a rich web application that fetches all its data using AJAX. It will be completely custom made using only a low level javascript library. The server back end is supposed to serve static content and javascript (basically the rich web application) and to provide a RESTful web service API (which I would like to implement using aforementioned framework).

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• is PHP itself transforming into a framework?

  - by Elzo Valugi

  At the beginning PHP was a scripting language. But after the introduction and improvement of OOP I see more and more objects added to the core. They started with SPL which grew a lot, now we have DOMDocument family, DateTime family which should be part of PECL, Pear or Zend Framework or implemented by each one of us. Shouldn't be php only for build-in functions and all these objects passed to something else? Example. DateTime class is part of the core and I see it very similar with Zend_Date.

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• Is it possible to register a user and submit a comment with one form with Wordpress?

  - by zack

  Is it possible to do both registering for an account and submit a comment at the same time? I want the user to be able to do this all on one page to ecourage the registration rather than be discouraged about typing something, not realizing they had to be registered and thus having to leave the page. I think that this could be done by adding register user action to the submit comment action, but not sure how to do it with the prebuilt wordpress add_action or do_action functions. Has anyone tried this, or know of any plug-ins that do this already? I searched but couldn't find anything helpful. Thanks.

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• Autorelease for CGMutablePathRef?

  - by huggie

  Hi, I am developing for iphone. I want to creating a mutable path via CGPathCreateMutable(), and I want to return it out of the function which creates it. I'm suppose to call a CGPathRelease() when I'm done with it. But since I'm returning it I wish to autorelease it. Since Quartz path is a C code (and doesn't look like an objective C object), is it correct that I cannot call autorelease on it? Edit: For others who stumble upon this question, the below advise is for C functions returning Core foundation objects only. For objective C methods returning Core foundation objects, see http://stackoverflow.com/questions/2901942/ownership-regarding-to-returned-quartz-objects

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