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  • no match for operator= using a std::vector

    - by Max
    I've got a class declared like this: class Level { private: std::vector<mapObject::MapObject> features; (...) }; and in one of its member functions I try to iterate through that vector like this: vector<mapObject::MapObject::iterator it; for(it=features.begin(); it<features.end(); it++) { /* loop code */ } This seems straightforward to me, but g++ gives me this error: src/Level.cpp:402: error: no match for ‘operator=’ in ‘it = ((const yarl::level::Level*)this)-yarl::level::Level::features.std::vector<_Tp, _Alloc::begin [with _Tp = yarl::mapObject::MapObject, _Alloc = std::allocator<yarl::mapObject::MapObject>]()’ /usr/include/c++/4.4/bits/stl_iterator.h:669: note: candidates are: __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector & __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector >::operator=(const __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*, ``std::vector<yarl::mapObject::MapObject, std::allocator<yarl::mapObject::MapObject> > >&) Anyone know why this is happening?

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  • Problem with operator ==

    - by CPPDev
    I am facing some problem with use of operator == in the following c++ program. #include < iostream> using namespace std; class A { public: A(char *b) { a = b; } A(A &c) { a = c.a; } bool operator ==(A &other) { return strcmp(a, other.a); } private: char *a; }; int main() { A obj("test"); A obj1("test1"); if(obj1 == A("test1")) { cout<<"This is true"<<endl; } } What's wrong with if(obj1 == A("test1")) line ?? Any help is appreciated.

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  • C++ overloading operator comma for variadic arguments

    - by uray
    is it possible to construct variadic arguments for function by overloading operator comma of the argument? i want to see an example how to do so.., maybe something like this: template <typename T> class ArgList { public: ArgList(const T& a); ArgList<T>& operator,(const T& a,const T& b); } //declaration void myFunction(ArgList<int> list); //in use: myFunction(1,2,3,4); //or maybe: myFunction(ArgList<int>(1),2,3,4);

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  • C# String Operator Overloading

    - by ScottSEA
    G'Day Mates - What is the right way (excluding the argument of whether it is advisable) to overload the string operators <, , <= and = ? I've tried it five ways to Sunday and I get various errors - my best shot was declaring a partial class and overloading from there, but it won't work for some reason. namespace System { public partial class String { public static Boolean operator <(String a, String b) { return a.CompareTo(b) < 0; } public static Boolean operator >(String a, String b) { return a.CompareTo(b) > 0; } } }

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  • An operator == whose parameters are non-const references

    - by Eduardo León
    I this post, I've seen this: class MonitorObjectString: public MonitorObject { // some other declarations friend inline bool operator==(/*const*/ MonitorObjectString& lhs, /*const*/ MonitorObjectString& rhs) { return lhs.fVal==rhs.fVal; } } Before we can continue, THIS IS VERY IMPORTANT: I am not questioning anyone's ability to code. I am just wondering why someone would need non-const references in a comparison. The poster of that question did not write that code. This was just in case. This is important too: I added both /*const*/s and reformatted the code. Now, we get back to the topic: I can't think of a sane use of the equality operator that lets you modify its by-ref arguments. Do you?

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  • Dynamic Operator Overloading on dict classes in Python

    - by Ishpeck
    I have a class that dynamically overloads basic arithmetic operators like so... import operator class IshyNum: def __init__(self, n): self.num=n self.buildArith() def arithmetic(self, other, o): return o(self.num, other) def buildArith(self): map(lambda o: setattr(self, "__%s__"%o,lambda f: self.arithmetic(f, getattr(operator, o))), ["add", "sub", "mul", "div"]) if __name__=="__main__": number=IshyNum(5) print number+5 print number/2 print number*3 print number-3 But if I change the class to inherit from the dictionary (class IshyNum(dict):) it doesn't work. I need to explicitly def __add__(self, other) or whatever in order for this to work. Why?

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  • Scala :: operator, how it works?

    - by Felix
    Hello Guys, in Scala, I can make a caseclass case class Foo(x:Int) and then put it in a list like so: List(Foo(42)) Now, nothing strange here. The following is strange to me. The operator :: is a function on a list, right? With any function with 1 argument in Scala, I can call it with infix notation. An example is 1 + 2 is a function (+) on the object Int. The class Foo I just defined does not have the :: operator, so how is the following possible: Foo(40) :: List(Foo(2)) ? In scala 2.8 rc1, I get the following output from the interactive prompt: scala> case class Foo(x:Int) defined class Foo scala> Foo(40) :: List(Foo(2)) res2: List[Foo] = List(Foo(40), Foo(2)) scala> I can go on and use it, but if someone can explain it I will be glad :)

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  • Passing operator as a parameter

    - by nacho4d
    Hi, I want to have a function that evaluates 2 bool vars (like a truth table) for example: since T | F : T then myfunc('t', 'f', ||); /*defined as: bool myfunc(char lv, char rv, ????)*/ should return true; how can I pass the third parameter? (I know is possible to pass it as a char* but then I will have to have another table to compare operator string and then do the operation which is something I would like to avoid) Is it possible to pass an operator like ^(XOR) or ||(OR) or &&(AND), etc in a function/method? Thanks in advance

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  • copy C'tor with operator= | C++

    - by user2266935
    I've got this code here: class DerivedClass : public BaseClass { SomeClass* a1; Someclass* a2; public: //constructors go here ~DerivedClass() { delete a1; delete a2;} // other functions go here .... }; My first question is as follows: Can I write an "operator=" to "DerivedClass" ? (if your answer is yes, could you show me how?) My second question is: If the answer to the above is yes, could you show me how to make an "copy c'tor" using the "operator=" that you wrote beforehand (if that is even possible)? Your help would be much appreciated !

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  • template; operator (int)

    - by Oops
    Hi, regarding my Point struct already mentioned here: http://stackoverflow.com/questions/2794369/template-class-ctor-against-function-new-c-standard is there a chance to replace the function toint() with a cast-operator (int)? namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; //umm??? template < typename U > Point< dims, U > operator U() const { Point< dims, U > ret; std::copy( X, X + dims, ret.X ); return ret; } //umm??? Point< dims, int > operator int() const { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } //OK Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } }; //struct Point template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } }; //namespace point int main(void) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 2, int > p2i = (int)p2d; //äähhm??? std::cout << p2d.str() << std::endl; char c; std::cin >> c; return 0; } I think the problem is here that C++ cannot distinguish between different return types? many thanks in advance. regards Oops

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  • Oracle logical standby fails with ORA-01919

    - by DCookie
    I have an Oracle logical standby database being managed via data guard. Just this morning the redo apply process began failing with an ORA-01919 error, indicating one of our application roles did not exist. However, I can see the role on both primary and standby databases. We also have a physical standby that has long since applied the redo where this is happening on the logical, without issue. I have opened an SR with Oracle. I was wondering if anyone out there has seen this before. I guess I should mention: Oracle 10.2.0.4, Win2003 Server SP2. UPDATE: So far, Oracle Support has not provided an answer. I thought I'd post here what I have learned so far. It appears that a grant of DBA on the primary host to a role works fine for users granted the role. It does not work on the logical standby. IOW: create role TEST; grant dba to TEST; grant TEST to auser; connect auser set role TEST; grant <existing role> to <existing user>; This works on the primary instance but fails on the logical. A workaround appears to be to grant each role on the primary to the role TEST with admin option in the logical: grant <existing role> to TEST with admin option; <== do this on the logical standby Then the command works on the logical standby.

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  • Removing extended partition without deleting logical in it

    - by HisDudeness
    I'm running a Linux-based laptop, and in order to multi-boot several distros in it, I created an extended partition which contains a bunch of logical ones with GParted. Now, after quite a long time with this setup, I've changed my mind because of the consequent lack of storing space for my data partition. Now I want to keep one distro alone like it's normal, and eventually have some other operating systems stored in external supports to plug in and use if I want. Obviously, also this partition I want to keep (and to enlarge a little too) is just a logical inside the extended I want to keep. For what concerns the number I'm ok, meaning I currently have this big distro dedicated extended, the swap and the data partitions, so there's space for another primary before I delete the extended, but I don't know how to delete it without touching the logical in it, I don't want to reinstall the system losing all changes and settings, and I don't want to keep an extended partition for a logical alone. How can I do? Do I have to create a new primary, copy the logical content in it and then delete everything? Will the system boot and maintain exactly all the features it has now? Or is there a way to convert an extended into a primary once it contains just one logical? Or can I directly move a logical out of an extended turning it into a primary? Or, again, am I screwed?

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  • T-4 Templates for ASP.NET Web Form Databound Control Friendly Logical Layers

    - by Mohammad Ashraful Alam
    I just released an open source project at codeplex, which includes a set of T-4 templates that will enable you to build ASP.NET Web Form Data Bound controls friendly testable logical layer based on Entity Framework 4.0 with just few clicks! In this open source project you will get Entity Framework 4.0 based T-4 templates for following types of logical layers: Data Access Layer: Entity Framework 4.0 provides excellent ORM data access layer. It also includes support for T-4 templates, as built-in code generation strategy in Visual Studio 2010, where we can customize default structure of data access layer based on Entity Framework. default structure of data access layer has been enhanced to get support for mock testing in Entity Framework 4.0 object model. Business Logic Layer: ASP.NET web form based data bound control friendly business logic layer, which will enable you few clicks to build data bound web applications on top of ASP.NET Web Form and Entity Framework 4.0 quickly with great support of mock testing. Download it to make your web development productive. Enjoy!

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  • null-coalescing operator or conditional operator

    - by rkrauter
    Which coding style do you prefer: object o = new object(); //string s1 = o ?? "Tom"; // Cannot implicitly convert type 'object' to 'string' CS0266 string s3 = Convert.ToString(o ?? "Tom"); string s2 = (o != null) ? o.ToString() : "Tom"; s2 or s3? Is it possible to make it shorter? s1 does not obviously work.

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  • Teaching logical/analytical thinking

    - by Joshua
    I have been trial running a club in which I teach programming for the past year and while they have progressed what they really lack is the most fundamental concept to programming, analytical thinking. As I now approach the second year of teaching to the children (aged 12 - 14) I am now realising that before I begin teaching them the syntax and how to actually program an app (or what they would rather, a game) I need to introduce them to analytical thinking first. I have already found Scratch and similar things such as Light-Bot and will most certainly be using the, to teach them how to implement their logical thinking but what I really need are some tips or articles on how to teach analytical thinking itself to children aged 12 - 14. What I'm looking for are some ideas on how to teach the kind of thinking that these kids will need in order to get them into programming, whether that be analytical, logical or critical. How and what should I teach them relating to the way their minds need to be wired when programming solutions to problems?

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  • Working with Reporting Services Filters – Part 2: The LIKE Operator

    - by smisner
    In the first post of this series, I introduced the use of filters within the report rather than in the query. I included a list of filter operators, and then focused on the use of the IN operator. As I mentioned in the previous post, the use of some of these operators is not obvious, so I'm going to spend some time explaining them as well as describing ways that you can use report filters in Reporting Services in this series of blog posts. Now let's look at the LIKE operator. If you write T-SQL queries, you've undoubtedly used the LIKE operator to produce a query using the % symbol as a wildcard for multiple characters like this: select * from DimProduct where EnglishProductName like '%Silver%' And you know that you can use the _ symbol as a wildcard for a single character like this: select * from DimProduct where EnglishProductName like '_L Mountain Frame - Black, 4_'   So when you encounter the LIKE operator in a Reporting Services filter, you probably expect it to work the same way. But it doesn't. You use the * symbol as a wildcard for multiple characters as shown here: Expression Data Type Operator Value [EnglishProductName] Text Like *Silver* Note that you don’t have to include quotes around the string that you use for comparison. Books Online has an example of using the % symbol as a wildcard for a single character, but I have not been able to successfully use this wildcard. If anyone has a working example, I’d love to see it!

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  • Which to use - "operator new" or "operator new[]" - to allocate a block of raw memory in C++?

    - by sharptooth
    My C++ program needs a block of uninitialized memory. In C I would use malloc() and later free(). In C++ I can either call ::operator new or ::operator new[] and ::operator delete or operator delete[] respectively later. Looks like both ::operator new and ::operator new[] have exactly the same signature and exactly the same behavior. The same for ::operator delete and ::operator delete[]. The only thing I shouldn't do is pairing operator new with operator delete[] and vice versa - undefined behavior. Other than that which pair do I choose and why?

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  • C++ operator new, object versions, and the allocation sizes

    - by mizubasho
    Hi. I have a question about different versions of an object, their sizes, and allocation. The platform is Solaris 8 (and higher). Let's say we have programs A, B, and C that all link to a shared library D. Some class is defined in the library D, let's call it 'classD', and assume the size is 100 bytes. Now, we want to add a few members to classD for the next version of program A, without affecting existing binaries B or C. The new size will be, say, 120 bytes. We want program A to use the new definition of classD (120 bytes), while programs B and C continue to use the old definition of classD (100 bytes). A, B, and C all use the operator "new" to create instances of D. The question is, when does the operator "new" know the amount of memory to allocate? Compile time or run time? One thing I am afraid of is, programs B and C expect classD to be and alloate 100 bytes whereas the new shared library D requires 120 bytes for classD, and this inconsistency may cause memory corruption in programs B and C if I link them with the new library D. In other words, the area for extra 20 bytes that the new classD require may be allocated to some other variables by program B and C. Is this assumption correct? Thanks for your help.

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  • Reflection and Operator Overloads in C#

    - by TenshiNoK
    Here's the deal. I've got a program that will load a given assembly, parse through all Types and their Members and compile a TreeView (very similar to old MSDN site) and then build HTML pages for each node in the TreeView. It basically takes a given assembly and allows the user to create their own MSDN-like library for it for documentation purposes. Here's the problem I've run into: whenever an operator overload is encounted in a defined class, reflection returns that as a "MethodInfo" with the name set to something like "op_Assign" or "op_Equality". I want to be able to capture these and list them properly, but I can't find anything in the MethodInfo object that is returned to accurately identify that I'm looking at an operator. I definitely don't want to just capture everything that starts with "op_", since that will most certainly (at some point) will pick up a method it's not supposed to. I know that other methods and properties that are "special cases" like this one have the "IsSpecialName" property set, but appearantly that's not the case with operators. I've been scouring the 'net and wracking my brain to two days trying to figure this one out, so any help will be greatly appreciated.

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  • No device file for partition on logical volume (Linux LVM)

    - by Brian
    I created a logical volume (scandata) containing a single ext3 partition. It is the only logical volume in its volume group (case4t). Said volume group is comprised by 3 physical volumes, which are three primary partitions on a single block device (/dev/sdb). When I created it, I could mount the partition via the block device /dev/mapper/case4t-scandatap1. Since last reboot the aforementioned block device file has disappeared. It may be of note -- I'm not sure -- that my superior (a college professor) had prompted this reboot by running sudo chmod -R [his name] /usr/bin, which obliterated all suid in its path, preventing the both of us from sudo-ing. That issue has been (temporarily) rectified via this operation. Now I'll cut the chatter and get started with the terminal dumps: $ sudo pvs; sudo vgs; sudo lvs Logging initialised at Sat Jan 8 11:42:34 2011 Set umask to 0077 Scanning for physical volume names PV VG Fmt Attr PSize PFree /dev/sdb1 case4t lvm2 a- 819.32G 0 /dev/sdb2 case4t lvm2 a- 866.40G 0 /dev/sdb3 case4t lvm2 a- 47.09G 0 Wiping internal VG cache Logging initialised at Sat Jan 8 11:42:34 2011 Set umask to 0077 Finding all volume groups Finding volume group "case4t" VG #PV #LV #SN Attr VSize VFree case4t 3 1 0 wz--n- 1.69T 0 Wiping internal VG cache Logging initialised at Sat Jan 8 11:42:34 2011 Set umask to 0077 Finding all logical volumes LV VG Attr LSize Origin Snap% Move Log Copy% Convert scandata case4t -wi-a- 1.69T Wiping internal VG cache $ sudo vgchange -a y Logging initialised at Sat Jan 8 11:43:14 2011 Set umask to 0077 Finding all volume groups Finding volume group "case4t" 1 logical volume(s) in volume group "case4t" already active 1 existing logical volume(s) in volume group "case4t" monitored Found volume group "case4t" Activated logical volumes in volume group "case4t" 1 logical volume(s) in volume group "case4t" now active Wiping internal VG cache $ ls /dev | grep case4t case4t $ ls /dev/mapper case4t-scandata control $ sudo fdisk -l /dev/case4t/scandata Disk /dev/case4t/scandata: 1860.5 GB, 1860584865792 bytes 255 heads, 63 sectors/track, 226203 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00049bf5 Device Boot Start End Blocks Id System /dev/case4t/scandata1 1 226203 1816975566 83 Linux $ sudo parted /dev/case4t/scandata print Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/case4t-scandata: 1861GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 32.3kB 1861GB 1861GB primary ext3 $ sudo fdisk -l /dev/sdb Disk /dev/sdb: 1860.5 GB, 1860593254400 bytes 255 heads, 63 sectors/track, 226204 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000081 Device Boot Start End Blocks Id System /dev/sdb1 1 106955 859116006 83 Linux /dev/sdb2 113103 226204 908491815 83 Linux /dev/sdb3 106956 113102 49375777+ 83 Linux Partition table entries are not in disk order $ sudo parted /dev/sdb print Model: DELL PERC 6/i (scsi) Disk /dev/sdb: 1861GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 32.3kB 880GB 880GB primary reiserfs 3 880GB 930GB 50.6GB primary 2 930GB 1861GB 930GB primary I find it a bit strange that partition one above is said to be reiserfs, or if it matters -- it was previously reiserfs, but LVM recognizes it as a PV. To reiterate, neither /dev/mapper/case4t-scandatap1 (which I had used previously) nor /dev/case4t/scandata1 (as printed by fdisk) exists. And /dev/case4t/scandata (no partition number) cannot be mounted: $sudo mount -t ext3 /dev/case4t/scandata /mnt/new mount: wrong fs type, bad option, bad superblock on /dev/mapper/case4t-scandata, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so All I get on syslog is: [170059.538137] VFS: Can't find ext3 filesystem on dev dm-0. Thanks in advance for any help you can offer, Brian P.S. I am on Ubuntu GNU/Linux 2.6.28-11-server (Jaunty) (out of date, I know -- that's on the laundry list).

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