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  • Why would one overload the && and & operator?

    - by acidzombie24
    The same question goes for | and ||. Why would one overload or 'use' the & and && operator? The only use i thought of are Bitwise Ands for int base types (but not float/decimals) using & logical short circuit for bools/functions that return bool. Using the && operator usually. I cant think of any classes that use those operators. Absolutely none. I know a class might support + (and not '-') which combine two strings together. I seen an object such as datetime overload '-' so two dates can be subtracted to make a timespan (obviously you cant add two dates) but i never seen &, &&, | and || used. Does anyone know of a use? In any language?

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  • Data Conversion in SQL Server

    Most of the time, you do not have to worry about implicit conversion in SQL expressions, or when assigning a value to a column. Just occasionally, though, you'll find that data gets truncated, queries run slowly, or comparisons just seem plain wrong. Robert Sheldon explains why you sometimes need to be very careful if you mix data types when manipulating values. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Combining two operators in Evil-mode Emacs

    - by Dyslexic Tangent
    In vim I've remapped > and < when in visual mode to >gv and <gv respectively, like so: vnoremap > >gv vnoremap < <gv Since my target for this question are folks experienced with emacs and not vim, what > and < do is indent/dedent visually selected text. What gv does is reselect the previously selected text. These maps cause > and < to indent/dedent and then reselect the previously selected text. I'm trying out emacs with evil-mode and I'd like to do the same, but I'm having some difficulty figuring out how, exactly, to accomplish the automatic reselection. It looks like I need to somehow call evil-shift-right and evil-visual-restore sequentially, but I don't know how to create a map that will do both, so I tried creating my own function which would call both sequentially and map that instead, but it didn't work, possibly due to the fact that both of them are defined, not as functions with defun but instead as operators with evil-define-operator. I tried creating my own operators: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-restore)) but that doesn't restore visual as expected. A stab in the dark gave me this: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) ('evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) ('evil-visual-restore)) but that selects one additional line whenever it is supposed to reselect. For now I've been using the following, which only has the problem where it reselects an additional line in the < operator. (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-make-selection beg end)) (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-make-selection beg end)) and I've mapped them: (define-key evil-visual-state-map ">" 'shift-right-reselect) (define-key evil-visual-state-map "<" 'shift-left-reselect) any help / pointers / tips would be greatly appreciated. Thanks in advance.

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  • Nagios3: Conditional operators for service checks?

    - by Dave
    I'm trying to setup Nagios to monitor my various using hostgroups to define 'machine roles', against which I run services to check the machines by role. However, I'd like to use conditional operators that would enable me to run the service check against an intersection of two host groups, rather than their unions... i.e. using &&, ||, or () operators. For example, imagine I have the following servers: www-eu: Linux WWW (Apache) server, in the EU www-us: Windows WWW (IIS) server, in the US (West coast) ftp-eu: Linux FTP server, in the EU ftp-us: Windows FTP server, in the US I would want to create the following host groups: US-Servers: www-us, ftp-us EU-Servers: www-eu, ftp-eu WWW-Servers: www-us, www-eu FTP-Servers: ftp-us, ftp-eu Now say I'm interested in checking the HTTP response time for my web servers. Then let's say this particular Nagios service is running from the US (West Coast), and that I have a command called *check_http_response_time*. This command will check the responsiveness of the HTTP server, which I can provide an argument which defines the max response time before raising critical. My command might look like: check_http_response_time $HOSTNAME$ 50 Now traditionally, I can run my checks by specifying a list of host or hostgroups. define service{ use local-service hostgroup_name WWW-Servers # Servers = www-us, www-eu servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } However, with the above service definition, given my Nagios service is in US West, I could reasonably expect that my EU server will return critical. Really, I want different thresholds for each region (50 for US West, 200 for EU.) I would have to permutate my service for each host and set their custom threshold, or alternatively permutate out my service groups by role & region (i.e. WWW-Servers-EU), and run my specific thresholds against those. Though the latter is better, both are much messier than I'd like... What I would love, and what this post is asking for, is a way to use hostgroups to perform an intersection using conditional logic, rather than a simple union. It might look like: define service{ use local-service hostgroup_name WWW-Servers && US-Servers servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } It then would run the check only against servers that are in both WWW-Servers and US-Servers, in my example, just www-us. The benefits of such a feature would be significant for Nagios services configured for large-scale. Is this feature available? If it isn't, will it be available in the future? Is there an alternative way to accomplish this given the most recent Nagios version? Any tips/suggestions are most appreciated! Dave

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  • What is the rationale to not allow overloading of C++ conversions operator with non-member function

    - by Vicente Botet Escriba
    C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From > operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration> operator boost::posix_time::ptime( const boost::chrono::time_point<Clock, Duration>& from) { using namespace boost; typedef chrono::time_point<Clock, Duration> time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast<duration_t>( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast<long>(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. For a more complete description of the problem, see here or on my Boost.Conversion library.. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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  • Cocos2d-x v3 invalid conversion from 'cocos2d::Layer* [on hold]

    - by Hammerh5
    Hello guys I'm learning cocos2d-x v3 right but most of the code that I can find is to the version 2. My specific error is this one, when I try to compile my cocos2s-x 3 project this error shows. invalid conversion from 'cocos2d::Layer to Game* [-fpermisive]* What I want to do is create a new game scene in the following code: //Game.cpp #include "Game.h" Scene* Game::scene() { scene *sc = CCScene::create(); sc->setTag(TAG_GAME_SCENE); const Game *g = Game::create(); //Here is where the conversions fails. sc->addChild(g, 0, TAG_GAME_LAYER); return sc; } Of course this is my header file //Game.h #include "cocos2d.h" #include "Mole.h" #include "AppDelegate.h" using namespace cocos2d; class Game: public cocos2d::Layer { cocos2d::CCArray *moles; float timeBetweenMoles, timeElapsed, increaseMolesAtTime, increaseElapsed, lastMoleHiTime; int molesAtOnce; cocos2d::CCSize s; bool isPaused; public: CCString *missSound, *hitSound; static cocos2d::Scene* scene(); virtual bool init(); void showMole(); void initializeGame(); void onEnterTransitionDidFinish(); void onExit(); void onTouchesBegan(const std::vector<cocos2d::Touch *> &touches, cocos2d::Event *event); void tick(float dt); cocos2d::CCArray* getMoles(bool isUp); //LAYER_CREATE_FUNC(Game); }; #endif /* GAME_H_ */ I don't know what's wrong I suppose this code works fine in Cocos2d-x v2. It's maybe some changes in the C++ version ?

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  • What is the most concise, unambiguous syntax for operator associated methods (for overloading etc.) that doesn't pollute the namespace?

    - by Doug Treadwell
    Python tends to add double underscores before its built-in or overloadable operator methods, like __add(), whereas C++ requires declaring overloaded operators as operator + (Thing& thing) { /* code */ } for example. Personally I like the operator syntax because it seems to be more explicit and keeps these operator overloading methods separated from other methods without introducing weird prefix notation. What are your thoughts? Also, what about the case of built-in methods that are needed for the programming language to work properly? Is name mangling (like adding __ prefix or sys or something) the best solution here? What do you think about having another type of method declaration, like ... "system method" for lack of creativity at the moment. So there would be two kinds of declarations: int method_name() { ... } system int method_name() { ... } ... and the call would need to be different to distinguish between them. obj.method_name(); vs obj:method_name(); perhaps, assuming a language where : can be unambiguously used in this situation. obj.method_name() vs obj.(system method_name)() Sure, the latter is ugly, but the idea is to make the common case simple and system stuff should be kept out of the way. Maybe the Objective-C notation of method calls? [obj method_name]? Are there more alternatives? Please make suggestions.

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  • Twitter search API VS Operators

    - by supermogx
    I've found this page about the Twitter search API and some operators : http://search.twitter.com/operators But is it possible to make a search like : All posts containing the words "ipod OR ipad" AND all posts containing the words "funny OR joke" ? Like : "happy AND hour" OR "ipod AND ipad" this doesn't look like it's possible.

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  • What exactly are administrative redexes after CPS conversion?

    - by eljenso
    In the context of Scheme and CPS conversion, I'm having a little trouble deciding what administrative redexes (lambdas) exactly are: all the lambda expressions that are introduced by the CPS conversion only the lambda expressions that are introduced by the CPS conversion but you wouldn't have written if you did the conversion "by hand" or through a smarter CPS-converter If possible, a good reference would be welcome.

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  • Raw Audio Conversion

    - by Walidix
    While, I'm reading gstreamer document I found this: " Audioconvert converts raw audio buffers between various possible formats. It supports integer to float conversion, width/depth conversion, signedness and endianness conversion and channel transformations." I only understand "depth" (bit number per sample) "signedness and endianness" (for data representation) And now, I'm looking for explanations of : "integer to float conversion" "width" "channel transformations" Thanks in advance

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  • conversion of a VMDK image with qemu-img failed with "error while reading sector 131072: Invalid argument"

    - by Erik Sjölund
    I tried to convert a VMDK image found in a OVA file to the QCOW2 format with the qemu-img command but it failed with the error message qemu-img: error while reading sector 131072: Invalid argument user@ubuntu:/tmp$ wget ftp://ftp.sanger.ac.uk/pub/databases/Pfam/vm/PfamWeb_20120124.ova user@ubuntu:/tmp$ tar xfv PfamWeb_20120124.ova PfamWeb_20120124_2.ovf PfamWeb_20120124_2.mf PfamWeb_20120124_2-disk1.vmdk user@ubuntu:/tmp$ qemu-img convert -O qcow2 PfamWeb_20120124_2-disk1.vmdk PfamWeb_20120124_2.qcow2 qemu-img: error while reading sector 131072: Invalid argument user@ubuntu:/tmp$ qemu-img --version | grep "qemu-img version" qemu-img version 1.0, Copyright (c) 2004-2008 Fabrice Bellard user@ubuntu:/tmp$ dpkg-query -f='${Version}\n' --show qemu-utils 1.0+noroms-0ubuntu14.1 user@ubuntu:/tmp$ cat /etc/issue Ubuntu 12.04.1 LTS \n \l How do I avoid the error?

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  • How do I overload an operator for an enumeration in C#?

    - by ChrisHDog
    I have an enumerated type that I would like to define the , <, =, and <= operators for. I know that these operators are implictly created on the basis of the enumerated type (as per the documentation) but I would like to explictly define these operators (for clarity, for control, to know how to do it, etc...) I was hoping I could do something like: public enum SizeType { Small = 0, Medium = 1, Large = 2, ExtraLarge = 3 } public SizeType operator >(SizeType x, SizeType y) { } But this doesn't seem to work ("unexpected toke") ... is this possible? It seems like it should be since there are implictly defined operators. Any suggestions?

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  • Infix to Postfix and unary/binary operators

    - by Jaapjan
    I have a piece of code that converts an infix expression to an expression tree in memory. This works just fine. There's just one small trouble. I just connect work out how to involve the unary operators correctly (the right associative ones). With the following infix expression : +1 + +2 - -3 - -4 I would expect an RPN of: 1+2++3-4-- Yet, none of the online infix-post converters I can find handle this example in the way I would expect. Does anyone have a clear explanation of handling right associative operators, specifically the binary ones that can be mistaken for the unary ones?

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  • How to modify a given class to use const operators

    - by zsero
    I am trying to solve my question regarding using push_back in more than one level. From the comments/answers it is clear that I have to: Create a copy operator which takes a const argument Modify all my operators to const But because this header file is given to me there is an operator what I cannot make into const. It is a simple: float & operator [] (int i) { return _item[i]; } In the given program, this operator is used to get and set data. My problem is that because I need to have this operator in the header file, I cannot turn all the other operators to const, what means I cannot insert a copy operator. How can I make all my operators into const, while preserving the functionality of the already written program? Here is the full declaration of the class: class Vector3f { float _item[3]; public: float & operator [] (int i) { return _item[i]; } Vector3f(float x, float y, float z) { _item[0] = x ; _item[1] = y ; _item[2] = z; }; Vector3f() {}; Vector3f & operator = ( const Vector3f& obj) { _item[0] = obj[0]; _item[1] = obj[1]; _item[2] = obj[2]; return *this; }; Vector3f & operator += ( const Vector3f & obj) { _item[0] += obj[0]; _item[1] += obj[1]; _item[2] += obj[2]; return *this; }; bool operator ==( const Vector3f & obj) { bool x = (_item[0] == obj[0]) && (_item[1] == obj[1]) && (_item[2] == obj[2]); return x; } // my copy operator Vector3f(const Vector3f& obj) { _item[0] += obj[0]; _item[1] += obj[1]; _item[2] += obj[2]; return this; } };

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  • Bitwise operators versus .NET abstractions for bit manipulation in C# prespective

    - by Leron
    I'm trying to get basic skills in working with bits using C#.NET. I posted an example yesterday with a simple problem that needs bit manipulation which led me to the fact that there are two main approaches - using bitwise operators or using .NET abstractions such as BitArray (Please let me know if there are more build-in tools for working with bits other than BitArray in .NET and how to find more info for them if there are?). I understand that bitwise operators work faster but using BitArray is something much more easier for me, but one thing I really try to avoid is learning bad practices. Even though my personal preferences are for the .NET abstraction(s) I want to know which i actually better to learn and use in a real program. Thinking about it I'm tempted to think that .NET abstractions are not that bad at, after all there must be reason to be there and maybe being a beginner it's more natural to learn the abstraction and later on improve my skills with low level operations, but this is just random thoughts.

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  • using operators and functions for sql report charts (visual studio 2010)

    - by user1682566
    I want to create some charts using sql reporting services. But i am unable to use a lot of functions and operators in combination with my data-fields the following work(Stroke-data type is decimal): > =Fields!Stroke.Value > =Sum(Fields!Stroke.Value) > =First(Fields!Stroke.Value) > =Last(Fields!Stroke.Value) > =2+2394.12 the following dont work: > =Fields!Stroke.Value + 2 > =CStr(Fields!Stroke.Value) > =CDbl(Fields!Stroke.Value) > =Fields!Stroke.Value / Fields!Stroke.Value > =Sum(Fields!Stroke.Value) * 2 all other operators and functions(using Fields!Stroke.Value) dont work too

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  • NASM shift operators

    - by Hudson Worden
    How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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  • Ternary operators and variable reassignment in PHP

    - by TomcatExodus
    I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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  • External hard drive FAT32 to NTFS conversion fails

    - by Pieter
    I'm trying to convert the FAT32 file system of an external hard drive to NTFS. Here's what happened: C:\Windows\system32>chkdsk G: The type of the file system is FAT32. Volume PIETEREXT created 3/19/2008 12:43 Volume Serial Number is 1806-2E30 Windows is verifying files and folders... File and folder verification is complete. Windows has scanned the file system and found no problems. No further action is required. 488,264,768 KB total disk space. 72,192 KB in 1,503 hidden files. 1,281,792 KB in 40,029 folders. 309,235,168 KB in 199,915 files. 177,675,584 KB are available. 32,768 bytes in each allocation unit. 15,258,274 total allocation units on disk. 5,552,362 allocation units available on disk. C:\Windows\system32>cd \ C:\>convert g: /fs:ntfs The type of the file system is FAT32. Enter current volume label for drive G: PIETEREXT Volume PIETEREXT created 3/19/2008 12:43 Volume Serial Number is 1806-2E30 Windows is verifying files and folders... File and folder verification is complete. Windows has scanned the file system and found no problems. No further action is required. 488,264,768 KB total disk space. 72,192 KB in 1,503 hidden files. 1,281,792 KB in 40,029 folders. 309,235,168 KB in 199,915 files. 177,675,584 KB are available. 32,768 bytes in each allocation unit. 15,258,274 total allocation units on disk. 5,552,362 allocation units available on disk. Determining disk space required for file system conversion... Total disk space: 488384001 KB Free space on volume: 177675584 KB Space required for conversion: 975155 KB Converting file system The conversion failed. G: was not converted to NTFS I looked at the TechNet page for my error, but after closing every app the conversion was still failing halfway through. Why does it keep failing? I kept an eye on Task Manager but it didn't look like my system resources were near depletion. I'm using Windows 8.

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