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• What am I calling?

  - by Knowing me knowing you

  Is there a way to check inside a fnc what is this fnc name? I'm working currently on LargeInt class and I've realized that code for oparator and operator< is almost identical so I would like to know what operator is calling me and react accordingly. Thank you.

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• safe dereferencing and deletion

  - by serejko

  Hi, I'm relatively new to C++ and OOP in general and currently trying to make such a class that allows to dereference and delete a dead or invalid pointer without any care of having undefined behavior or program fault in result, and I want to ask you is it a good idea and is there something similar which is already implemented by someone else? or maybe I'm doing something completely wrong? I've just started making it and here is the code I currently have: template<class T> class SafeDeref { public: T& operator *() { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) return *this; return theDefaultObject; } T* operator ->() { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) return this; return &theDefaultObject; } void* operator new(size_t size) { void* ptr = malloc(size * sizeof(T)); if (ptr != 0) theStore.insert(reinterpret_cast<T*>(ptr)); return ptr; } void operator delete(void* ptr) { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) { theStore.erase(it); free(ptr); } } protected: static bool isInStore(T* ptr) { return theStore.find(ptr) != theStore.end(); } private: static T theDefaultObject; static hash_set<T*> theStore; }; The idea is that each class with the safe dereference should be inherited from it like this: class Foo : public SafeDeref<Foo> { void doSomething(); }; So... Any advices? Thanks in advance. P.S. If you're wondering why I need this... well, I'm creating a set of native functions for some scripting environment, and all of them use pointers to internally allocated objects as handles to them and they're able to delete them as well (input data can be wrong), so this is kinda protection from damaging host application's memory And I really sorry for my bad English

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• C++ require that one template type is derived from the other

  - by Will

  In a comparison operator: template<class R1, class R2> bool operator==(Manager<R1> m1, Manager<R2> m2) { return p1.internal_field == p2.internal_field; } Is there any way I could enforce that R1 and R2 must have a supertype or subtype relation? That is, I'd like to allow either R1 to be derived from R2, or R2 to be derived from R1, but disallow the comparison if R1 and R2 are unrelated types.

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• ? and function javascript

  - by Rixius

  is there any way to map the ? key to the function keyword? so that these work: var rFalse = ?() { return false; } (?(){ var str = "i'm in a closure"; }()); window.onload = ?() { alert('window loaded'); } I know that they are attempting to put a shortened function keyword in ecmascript v6, but I'm wondering if it is possible to do it now.

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• A Good Developer is So Hard to Find

  - by James Michael Hare

  Let me start out by saying I want to damn the writers of the Toughest Developer Puzzle Ever – 2. It is eating every last shred of my free time! But as I've been churning through each puzzle and marvelling at the brain teasers and trivia within, I began to think about interviewing developers and why it seems to be so hard to find good ones.  The problem is, it seems like no matter how hard we try to find the perfect way to separate the chaff from the wheat, inevitably someone will get hired who falls far short of expectations or someone will get passed over for missing a piece of trivia or a tricky brain teaser that could have been an excellent team member.   In shops that are primarily software-producing businesses or other heavily IT-oriented businesses (Microsoft, Amazon, etc) there often exists a much tighter bond between HR and the hiring development staff because development is their life-blood. Unfortunately, many of us work in places where IT is viewed as a cost or just a means to an end. In these shops, too often, HR and development staff may work against each other due to differences in opinion as to what a good developer is or what one is worth.  It seems that if you ask two different people what makes a good developer, often you will get three different opinions.   With the exception of those shops that are purely development-centric (you guys have it much easier!), most other shops have management who have very little knowledge about the development process.  Their view can often be that development is simply a skill that one learns and then once aquired, that developer can produce widgets as good as the next like workers on an assembly-line floor.  On the other side, you have many developers that feel that software development is an art unto itself and that the ability to create the most pure design or know the most obscure of keywords or write the shortest-possible obfuscated piece of code is a good coder.  So is it a skill?  An Art?  Or something entirely in between?   Saying that software is merely a skill and one just needs to learn the syntax and tools would be akin to saying anyone who knows English and can use Word can write a 300 page book that is accurate, meaningful, and stays true to the point.  This just isn't so.  It takes more than mere skill to take words and form a sentence, join those sentences into paragraphs, and those paragraphs into a document.  I've interviewed candidates who could answer obscure syntax and keyword questions and once they were hired could not code effectively at all.  So development must be more than a skill.   But on the other end, we have art.  Is development an art?  Is our end result to produce art?  I can marvel at a piece of code -- see it as concise and beautiful -- and yet that code most perform some stated function with accuracy and efficiency and maintainability.  None of these three things have anything to do with art, per se.  Art is beauty for its own sake and is a wonderful thing.  But if you apply that same though to development it just doesn't hold.  I've had developers tell me that all that matters is the end result and how you code it is entirely part of the art and I couldn't disagree more.  Yes, the end result, the accuracy, is the prime criteria to be met.  But if code is not maintainable and efficient, it would be just as useless as a beautiful car that breaks down once a week or that gets 2 miles to the gallon.  Yes, it may work in that it moves you from point A to point B and is pretty as hell, but if it can't be maintained or is not efficient, it's not a good solution.  So development must be something less than art.   In the end, I think I feel like development is a matter of craftsmanship.  We use our tools and we use our skills and set about to construct something that satisfies a purpose and yet is also elegant and efficient.  There is skill involved, and there is an art, but really it boils down to being able to craft code.  Crafting code is far more than writing code.  Anyone can write code if they know the syntax, but so few people can actually craft code that solves a purpose and craft it well.  So this is what I want to find, I want to find code craftsman!  But how?   I used to ask coding-trivia questions a long time ago and many people still fall back on this.  The thought is that if you ask the candidate some piece of coding trivia and they know the answer it must follow that they can craft good code.  For example:   What C++ keyword can be applied to a class/struct field to allow it to be changed even from a const-instance of that class/struct?  (answer: mutable)   So what do we prove if a candidate can answer this?  Only that they know what mutable means.  One would hope that this would infer that they'd know how to use it, and more importantly when and if it should ever be used!  But it rarely does!  The problem with triva questions is that you will either: Approve a really good developer who knows what some obscure keyword is (good) Reject a really good developer who never needed to use that keyword or is too inexperienced to know how to use it (bad) Approve a really bad developer who googled "C++ Interview Questions" and studied like hell but can't craft (very bad) Many HR departments love these kind of tests because they are short and easy to defend if a legal issue arrises on hiring decisions.  After all it's easy to say a person wasn't hired because they scored 30 out of 100 on some trivia test.  But unfortunately, you've eliminated a large part of your potential developer pool and possibly hired a few duds.  There are times I've hired candidates who knew every trivia question I could throw out them and couldn't craft.  And then there are times I've interviewed candidates who failed all my trivia but who I took a chance on who were my best finds ever.    So if not trivia, then what?  Brain teasers?  The thought is, these type of questions measure the thinking power of a candidate.  The problem is, once again, you will either: Approve a good candidate who has never heard the problem and can solve it (good) Reject a good candidate who just happens not to see the "catch" because they're nervous or it may be really obscure (bad) Approve a candidate who has studied enough interview brain teasers (once again, you can google em) to recognize the "catch" or knows the answer already (bad). Once again, you're eliminating good candidates and possibly accepting bad candidates.  In these cases, I think testing someone with brain teasers only tests their ability to answer brain teasers, not the ability to craft code. So how do we measure someone's ability to craft code?  Here's a novel idea: have them code!  Give them a computer and a compiler, or a whiteboard and a pen, or paper and pencil and have them construct a piece of code.  It just makes sense that if we're going to hire someone to code we should actually watch them code.  When they're done, we can judge them on several criteria: Correctness - does the candidate's solution accurately solve the problem proposed? Accuracy - is the candidate's solution reasonably syntactically correct? Efficiency - did the candidate write or use the more efficient data structures or algorithms for the job? Maintainability - was the candidate's code free of obfuscation and clever tricks that diminish readability? Persona - are they eager and willing or aloof and egotistical?  Will they work well within your team? It may sound simple, or it may sound crazy, but when I'm looking to hire a developer, I want to see them actually develop well-crafted code.

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• Convert C++Builder AnsiString to std::string via boost::lexical_cast

  - by David Klein

  For a school assignment I have to implement a project in C++ using Borland C++ Builder. As the VCL uses AnsiString for all GUI Components I have to convert all of my std::strings to AnsiString for the sake of displaying. std::string inp = "Hello world!"; AnsiString outp(inp.c_str()); works of course but is a bit tedious to write and code duplication I want to avoid. As we use Boost in other contexts I decided to provide some helper functions go get boost::lexical_cast to work with AnsiString. Here is my implementation so far: std::istream& operator>>(std::istream& istr, AnsiString& str) { istr.exceptions(std::ios::badbit | std::ios::failbit | std::ios::eofbit); std::string s; std::getline(istr,s); str = AnsiString(s.c_str()); return istr; } In the beginning I got Access Violation after Access Violation but since I added the .exceptions() stuff the picture gets clearer. When the conversion is performed I get the following Exception: ios_base::eofbit set [Runtime Error/std::ios_base::failure] Does anyone have an idea how to fix it and can explain why the error occurs? My C++ experience is very limited. The conversion routine the other way round would be: std::ostream& operator<<(std::ostream& ostr,const AnsiString& str) { ostr << (str.c_str()); return ostr; } Maybe someone will spot an error here too :) With best regards! Edit: At the moment I'm using the edited version of Jem, it works in the beginning. After a while of using the programm the Borland Codeguard mentions some pointer arithmetic in already freed regions. Any ideas how this could be related? The Codeguard log (I'm using the german version, translations marked with stars): ------------------------------------------ Fehler 00080. 0x104230 (r) (Thread 0x07A4): Zeigerarithmetik in freigegebenem Speicher: 0x0241A238-0x0241A258. **(pointer arithmetic in freed region)** | d:\program files\borland\bds\4.0\include\dinkumware\sstream Zeile 126: | { // not first growth, adjust pointers | _Seekhigh = _Seekhigh - _Mysb::eback() + _Ptr; |> _Mysb::setp(_Mysb::pbase() - _Mysb::eback() + _Ptr, | _Mysb::pptr() - _Mysb::eback() + _Ptr, _Ptr + _Newsize); | if (_Mystate & _Noread) Aufrufhierarchie: **(stack-trace)** 0x00411731(=FOSChampion.exe:0x01:010731) d:\program files\borland\bds\4.0\include\dinkumware\sstream#126 0x00411183(=FOSChampion.exe:0x01:010183) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#465 0x0040933D(=FOSChampion.exe:0x01:00833D) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#151 0x00405988(=FOSChampion.exe:0x01:004988) d:\program files\borland\bds\4.0\include\dinkumware\ostream#679 0x00405759(=FOSChampion.exe:0x01:004759) D:\Projekte\Schule\foschamp\src\Server\Ansistringkonverter.h#31 0x004080C9(=FOSChampion.exe:0x01:0070C9) D:\Projekte\Schule\foschamp\lib\boost_1_34_1\boost/lexical_cast.hpp#151 Objekt (0x0241A238) [Größe: 32 Byte] war erstellt mit new **(Object was created with new)** | d:\program files\borland\bds\4.0\include\dinkumware\xmemory Zeile 28: | _Ty _FARQ *_Allocate(_SIZT _Count, _Ty _FARQ *) | { // allocate storage for _Count elements of type _Ty |> return ((_Ty _FARQ *)::operator new(_Count * sizeof (_Ty))); | } | Aufrufhierarchie: **(stack-trace)** 0x0040ED90(=FOSChampion.exe:0x01:00DD90) d:\program files\borland\bds\4.0\include\dinkumware\xmemory#28 0x0040E194(=FOSChampion.exe:0x01:00D194) d:\program files\borland\bds\4.0\include\dinkumware\xmemory#143 0x004115CF(=FOSChampion.exe:0x01:0105CF) d:\program files\borland\bds\4.0\include\dinkumware\sstream#105 0x00411183(=FOSChampion.exe:0x01:010183) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#465 0x0040933D(=FOSChampion.exe:0x01:00833D) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#151 0x00405988(=FOSChampion.exe:0x01:004988) d:\program files\borland\bds\4.0\include\dinkumware\ostream#679 Objekt (0x0241A238) war Gelöscht mit delete **(Object was deleted with delete)** | d:\program files\borland\bds\4.0\include\dinkumware\xmemory Zeile 138: | void deallocate(pointer _Ptr, size_type) | { // deallocate object at _Ptr, ignore size |> ::operator delete(_Ptr); | } | Aufrufhierarchie: **(stack-trace)** 0x004044C6(=FOSChampion.exe:0x01:0034C6) d:\program files\borland\bds\4.0\include\dinkumware\xmemory#138 0x00411628(=FOSChampion.exe:0x01:010628) d:\program files\borland\bds\4.0\include\dinkumware\sstream#111 0x00411183(=FOSChampion.exe:0x01:010183) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#465 0x0040933D(=FOSChampion.exe:0x01:00833D) d:\program files\borland\bds\4.0\include\dinkumware\streambuf#151 0x00405988(=FOSChampion.exe:0x01:004988) d:\program files\borland\bds\4.0\include\dinkumware\ostream#679 0x00405759(=FOSChampion.exe:0x01:004759) D:\Projekte\Schule\foschamp\src\Server\Ansistringkonverter.h#31 ------------------------------------------ Ansistringkonverter.h is the file with the posted operators and line 31 is: std::ostream& operator<<(std::ostream& ostr,const AnsiString& str) { ostr << (str.c_str()); **(31)** return ostr; } Thanks for your help :)

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• C#/.NET Little Wonders: Comparer&lt;T&gt;.Default

  - by James Michael Hare

  I’ve been working with a wonderful team on a major release where I work, which has had the side-effect of occupying most of my spare time preparing, testing, and monitoring.  However, I do have this Little Wonder tidbit to offer today. Introduction The IComparable<T> interface is great for implementing a natural order for a data type.  It’s a very simple interface with a single method: 1: public interface IComparer<in T> 2: { 3: // Compare two instances of same type. 4: int Compare(T x, T y); 5: }  So what do we expect for the integer return value?  It’s a pseudo-relative measure of the ordering of x and y, which returns an integer value in much the same way C++ returns an integer result from the strcmp() c-style string comparison function: If x == y, returns 0. If x > y, returns > 0 (often +1, but not guaranteed) If x < y, returns < 0 (often –1, but not guaranteed) Notice that the comparison operator used to evaluate against zero should be the same comparison operator you’d use as the comparison operator between x and y.  That is, if you want to see if x > y you’d see if the result > 0. The Problem: Comparing With null Can Be Messy This gets tricky though when you have null arguments.  According to the MSDN, a null value should be considered equal to a null value, and a null value should be less than a non-null value.  So taking this into account we’d expect this instead: If x == y (or both null), return 0. If x > y (or y only is null), return > 0. If x < y (or x only is null), return < 0. But here’s the problem – if x is null, what happens when we attempt to call CompareTo() off of x? 1: // what happens if x is null? 2: x.CompareTo(y); It’s pretty obvious we’ll get a NullReferenceException here.  Now, we could guard against this before calling CompareTo(): 1: int result; 2:  3: // first check to see if lhs is null. 4: if (x == null) 5: { 6: // if lhs null, check rhs to decide on return value. 7: if (y == null) 8: { 9: result = 0; 10: } 11: else 12: { 13: result = -1; 14: } 15: } 16: else 17: { 18: // CompareTo() should handle a null y correctly and return > 0 if so. 19: result = x.CompareTo(y); 20: } Of course, we could shorten this with the ternary operator (?:), but even then it’s ugly repetitive code: 1: int result = (x == null) 2: ? ((y == null) ? 0 : -1) 3: : x.CompareTo(y); Fortunately, the null issues can be cleaned up by drafting in an external Comparer.  The Soltuion: Comparer<T>.Default You can always develop your own instance of IComparer<T> for the job of comparing two items of the same type.  The nice thing about a IComparer is its is independent of the things you are comparing, so this makes it great for comparing in an alternative order to the natural order of items, or when one or both of the items may be null. 1: public class NullableIntComparer : IComparer<int?> 2: { 3: public int Compare(int? x, int? y) 4: { 5: return (x == null) 6: ? ((y == null) ? 0 : -1) 7: : x.Value.CompareTo(y); 8: } 9: }  Now, if you want a custom sort -- especially on large-grained objects with different possible sort fields -- this is the best option you have.  But if you just want to take advantage of the natural ordering of the type, there is an easier way.  If the type you want to compare already implements IComparable<T> or if the type is System.Nullable<T> where T implements IComparable, there is a class in the System.Collections.Generic namespace called Comparer<T> which exposes a property called Default that will create a singleton that represents the default comparer for items of that type.  For example: 1: // compares integers 2: var intComparer = Comparer<int>.Default; 3:  4: // compares DateTime values 5: var dateTimeComparer = Comparer<DateTime>.Default; 6:  7: // compares nullable doubles using the null rules! 8: var nullableDoubleComparer = Comparer<double?>.Default;  This helps you avoid having to remember the messy null logic and makes it to compare objects where you don’t know if one or more of the values is null. This works especially well when creating say an IComparer<T> implementation for a large-grained class that may or may not contain a field.  For example, let’s say you want to create a sorting comparer for a stock open price, but if the market the stock is trading in hasn’t opened yet, the open price will be null.  We could handle this (assuming a reasonable Quote definition) like: 1: public class Quote 2: { 3: // the opening price of the symbol quoted 4: public double? Open { get; set; } 5:  6: // ticker symbol 7: public string Symbol { get; set; } 8:  9: // etc. 10: } 11:  12: public class OpenPriceQuoteComparer : IComparer<Quote> 13: { 14: // Compares two quotes by opening price 15: public int Compare(Quote x, Quote y) 16: { 17: return Comparer<double?>.Default.Compare(x.Open, y.Open); 18: } 19: } Summary Defining a custom comparer is often needed for non-natural ordering or defining alternative orderings, but when you just want to compare two items that are IComparable<T> and account for null behavior, you can use the Comparer<T>.Default comparer generator and you’ll never have to worry about correct null value sorting again.     Technorati Tags: C#,.NET,Little Wonders,BlackRabbitCoder,IComparable,Comparer

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• std::vector optimisation required

  - by marcp

  I've written a routine that uses std::vector<double> rather heavily. It runs rather slowly and AQTime seems to imply that I am constructing mountains of vectors but I'm not sure why I would be. For some context, my sample run iterates 10 times. Each iteration copies 3 c arrays of ~400 points into vectors and creates 3 new same sized vectors for output. Each output point might be the result of summing up to 20 points from 2 of the input vectors, which works out to a worst case of 10*400*3*2*20 = 480,000 dereferences. Incredibly the profiler indicates that some of the std:: methods are being called 46 MILLION times. I suspect I'm doing something wrong! Some code: vector<double>gdbChannel::GetVector() { if (fHaveDoubleData & (fLength > 0)) { double * pD = getDoublePointer(); vector<double>v(pD, pD + fLength); return v; } else { throw(Exception("attempt to retrieve vector on empty line")); ; } } void gdbChannel::SaveVector(GX_HANDLE _hLine, const vector<double> & V) { if (hLine != _hLine) { GetLine(_hLine, V.size(), true); } GX_DOUBLE * pData = getDoublePointer(); memcpy(pData, &V[0], V.size()*sizeof(V[0])); ReplaceData(); } ///This routine gets called 10 times bool SpecRatio::DoWork(GX_HANDLE_PTR pLine) { if (!(hKin.GetLine(*pLine, true) && hUin.GetLine(*pLine, true) && hTHin.GetLine(*pLine, true))) { return true; } vector<double>vK = hKin.GetVector(); vector<double>vU = hUin.GetVector(); vector<double>vTh = hTHin.GetVector(); if ((vK.size() == 0) || (vU.size() == 0) || (vTh.size() == 0)) { return true; } ///TODO: confirm all vectors the same lenghth len = vK.size(); vUK.clear(); // these 3 vectors are declared as private class members vUTh.clear(); vThK.clear(); vUK.reserve(len); vUTh.reserve(len); vThK.reserve(len); // TODO: ensure everything is same fidincr, fidstart and length for (int i = 0; i < len; i++) { if (vK.at(i) < MinK) { vUK.push_back(rDUMMY); vUTh.push_back(rDUMMY); vThK.push_back(rDUMMY); } else { vUK.push_back(RatioPoint(vU, vK, i, UMin, KMin)); vUTh.push_back(RatioPoint(vU, vTh, i, UMin, ThMin)); vThK.push_back(RatioPoint(vTh, vK, i, ThMin, KMin)); } } hUKout.setFidParams(hKin); hUKout.SaveVector(*pLine, vUK); hUTHout.setFidParams(hKin); hUTHout.SaveVector(*pLine, vUTh); hTHKout.setFidParams(hKin); hTHKout.SaveVector(*pLine, vThK); return TestError(); } double SpecRatio::VValue(vector<double>V, int Index) { double result; if ((Index < 0) || (Index >= len)) { result = 0; } else { try { result = V.at(Index); if (OasisUtils::isDummy(result)) { result = 0; } } catch (out_of_range) { result = 0; } } return result; } double SpecRatio::RatioPoint(vector<double>Num, vector<double>Denom, int Index, double NumMin, double DenomMin) { double num = VValue(Num, Index); double denom = VValue(Denom, Index); int s = 0; // Search equalled 10 in this case while (((num < NumMin) || (denom < DenomMin)) && (s < Search)) { num += VValue(Num, Index - s) + VValue(Num, Index + s); denom += VValue(Denom, Index - s) + VValue(Denom, Index + s); s++; } if ((num < NumMin) || (denom < DenomMin)) { return rDUMMY; } else { return num / denom; } } The top AQTime offenders are: std::_Uninit_copy , double *, std::allocator 3.65 secs and 115731 Hits std::_Construct 1.69 secs and 46450637 Hits std::_Vector_const_iterator ::operator !=1.66 secs and 46566395 Hits and so on... std::allocator<double>::construct, operator new, std::_Vector_const_iterator<double, std::allocator<double> >::operator ++, std::_Vector_const_iterator<double, std::allocator<double> >::operator * std::_Vector_const_iterator<double, std::allocator<double> >::operator == each get called over 46 million times. I'm obviously doing something wrong to cause all these objects to be created. Can anyone see my error(s)?

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• Adapting non-iterable containers to be iterated via custom templatized iterator

  - by DAldridge

  I have some classes, which for various reasons out of scope of this discussion, I cannot modify (irrelevant implementation details omitted): class Foo { /* ... irrelevant public interface ... */ }; class Bar { public: Foo& get_foo(size_t index) { /* whatever */ } size_t size_foo() { /* whatever */ } }; (There are many similar 'Foo' and 'Bar' classes I'm dealing with, and it's all generated code from elsewhere and stuff I don't want to subclass, etc.) [Edit: clarification - although there are many similar 'Foo' and 'Bar' classes, it is guaranteed that each "outer" class will have the getter and size methods. Only the getter method name and return type will differ for each "outer", based on whatever it's "inner" contained type is. So, if I have Baz which contains Quux instances, there will be Quux& Baz::get_quux(size_t index), and size_t Baz::size_quux().] Given the design of the Bar class, you cannot easily use it in STL algorithms (e.g. for_each, find_if, etc.), and must do imperative loops rather than taking a functional approach (reasons why I prefer the latter is also out of scope for this discussion): Bar b; size_t numFoo = b.size_foo(); for (int fooIdx = 0; fooIdx < numFoo; ++fooIdx) { Foo& f = b.get_foo(fooIdx); /* ... do stuff with 'f' ... */ } So... I've never created a custom iterator, and after reading various questions/answers on S.O. about iterator_traits and the like, I came up with this (currently half-baked) "solution": First, the custom iterator mechanism (NOTE: all uses of 'function' and 'bind' are from std::tr1 in MSVC9): // Iterator mechanism... template <typename TOuter, typename TInner> class ContainerIterator : public std::iterator<std::input_iterator_tag, TInner> { public: typedef function<TInner& (size_t)> func_type; ContainerIterator(const ContainerIterator& other) : mFunc(other.mFunc), mIndex(other.mIndex) {} ContainerIterator& operator++() { ++mIndex; return *this; } bool operator==(const ContainerIterator& other) { return ((mFunc.target<TOuter>() == other.mFunc.target<TOuter>()) && (mIndex == other.mIndex)); } bool operator!=(const ContainerIterator& other) { return !(*this == other); } TInner& operator*() { return mFunc(mIndex); } private: template<typename TOuter, typename TInner> friend class ContainerProxy; ContainerIterator(func_type func, size_t index = 0) : mFunc(func), mIndex(index) {} function<TInner& (size_t)> mFunc; size_t mIndex; }; Next, the mechanism by which I get valid iterators representing begin and end of the inner container: // Proxy(?) to the outer class instance, providing a way to get begin() and end() // iterators to the inner contained instances... template <typename TOuter, typename TInner> class ContainerProxy { public: typedef function<TInner& (size_t)> access_func_type; typedef function<size_t ()> size_func_type; typedef ContainerIterator<TOuter, TInner> iter_type; ContainerProxy(access_func_type accessFunc, size_func_type sizeFunc) : mAccessFunc(accessFunc), mSizeFunc(sizeFunc) {} iter_type begin() const { size_t numItems = mSizeFunc(); if (0 == numItems) return end(); else return ContainerIterator<TOuter, TInner>(mAccessFunc, 0); } iter_type end() const { size_t numItems = mSizeFunc(); return ContainerIterator<TOuter, TInner>(mAccessFunc, numItems); } private: access_func_type mAccessFunc; size_func_type mSizeFunc; }; I can use these classes in the following manner: // Sample function object for taking action on an LMX inner class instance yielded // by iteration... template <typename TInner> class SomeTInnerFunctor { public: void operator()(const TInner& inner) { /* ... whatever ... */ } }; // Example of iterating over an outer class instance's inner container... Bar b; /* assume populated which contained items ... */ ContainerProxy<Bar, Foo> bProxy( bind(&Bar::get_foo, b, _1), bind(&Bar::size_foo, b)); for_each(bProxy.begin(), bProxy.end(), SomeTInnerFunctor<Foo>()); Empirically, this solution functions correctly (minus any copy/paste or typos I may have introduced when editing the above for brevity). So, finally, the actual question: I don't like requiring the use of bind() and _1 placeholders, etcetera by the caller. All they really care about is: outer type, inner type, outer type's method to fetch inner instances, outer type's method to fetch count inner instances. Is there any way to "hide" the bind in the body of the template classes somehow? I've been unable to find a way to separately supply template parameters for the types and inner methods separately... Thanks! David

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• SQL SERVER – Fix : Error : 3117 : The log or differential backup cannot be restored because no files

  - by pinaldave

  I received the following email from one of my readers. Dear Pinal, I am new to SQL Server and our regular DBA is on vacation. Our production database had some problem and I have just restored full database backup to production server. When I try to apply log back I am getting following error. I am sure, this is valid log backup file. Screenshot is attached. [Few other details regarding server/ip address removed] Msg 3117, Level 16, State 1, Line 1 The log or differential backup cannot be restored because no files are ready to roll forward. Msg 3013, Level 16, State 1, Line 1 RESTORE LOG is terminating abnormally. Screenshot attached. [Removed as it contained live IP address] Please help immediately. Well I have answered this question in my earlier post, 2 years ago, over here SQL SERVER – Fix : Error : Msg 3117, Level 16, State 4 The log or differential backup cannot be restored because no files are ready to rollforward. However, I will try to explain it a little more this time. For SQL Server database to be used it should in online state. There are multiple states of SQL Server Database. ONLINE (Available – online for data) OFFLINE RESTORING RECOVERING RECOVERY PENDING SUSPECT EMERGENCY (Limited Availability) If the database is online, it means it is active and in operational mode. It will not make sense to apply further log from backup if the operations have continued on this database. The common practice during the backup restore process is to specify the keyword RECOVERY when the database is restored. When RECOVERY keyword is specified, the SQL Server brings back the database online and will not accept any further log backups. However, if you want to restore more than one backup files, i.e. after restoring the full back up if you want to apply further differential or log backup you cannot do that when database is online and already active. You need to have your database in the state where it can further accept the backup data and not the online data request. If the SQL Server is online and also accepts database backup file, then there can be data inconsistency. This is the reason that when there are more than one database backup files to be restored, one has to restore the database with NO RECOVERY keyword in the RESTORE operation. I suggest you all to read one more post written by me earlier. In this post, I explained the time line with image and graphic SQL SERVER – Backup Timeline and Understanding of Database Restore Process in Full Recovery Model. Sample Code for reference: RESTORE DATABASE AdventureWorks FROM DISK = 'C:\AdventureWorksFull.bak' WITH NORECOVERY; RESTORE DATABASE AdventureWorks FROM DISK = 'C:\AdventureWorksDiff.bak' WITH RECOVERY; In this post, I am not trying to cover complete backup and recovery. I am just attempting to address one type of error and its resolution. Please test these scenarios on the development server. Playing with live database backup and recovery is always very crucial and needs to be properly planned. Leave a comment here if you need help with this subject. Similar Post: SQL SERVER – Restore Sequence and Understanding NORECOVERY and RECOVERY Note: We will cover Standby Server maintenance and Recovery in another blog post and it is intentionally, not covered this post. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Backup and Restore, SQL Error Messages, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• So No TECH job so far.

  - by Ratman21

  O I found some temp work for the US Census and I have managed to keep the house (so far) but, it looks like I/we are going to have to do a short sale and the temp job will be ending soon.   On top of that it looks like the unemployment fund for me is drying up. I will have about one month left after the Census job is done. I am now down to Appling for work at the KFC.   This is type a work I started with, before I was a tech geek and really I didn’t think I would be doing this kind of work in my later years but, I have a wife and kid. So I got to suck it up and do it.   Oh and here is my new resume…go ahead I know you want to tare it up. I really don’t care any more.   Scott L. Newman 45219 Dutton Way, Callahan, FL32011 H: (904)879-4880 C: (352)356-0945 E: [email protected] Web:  http://beingscottnewman.webs.com/                                                       ______                                                                                 OBJECTIVE To obtain a Network or Technical support position     KEYWORD SUMMARY CompTIA A+, Network+, and Security+ Certified., Network Operation, Technical Support, Client/Vendor Relations, Networking/Administration, Cisco Routers/Switches, Helpdesk, Microsoft Office Suite, Website Design/Dev./Management, Frame Relay, ISDN, Windows NT/98/XP, Visio, Inventory Management, CICS, Programming, COBOL IV, Assembler, RPG   QUALIFICATIONS SUMMARY Twenty years’ experience in computer operations, technical support, and technical writing. Also have two and half years’ experience in internet / intranet operations.   PROFESSIONAL EXPERIENCE October 2009 – Present*   Volunteer Web site and PC technician – Part time       True Faith Christian Fellowship Church – Callahan, FL, Project: Create and maintain web site for Church to give it a worldwide exposure Aug 2008 – September 2009:* Volunteer Church sound and video technician – Part time      Thomas Creek Baptist Church – Callahan, FL   *Note Jobs were for the learning and/or keeping updated on skills, while looking for a tech job and training for new skills.   February 2005 to October 2008: Client Server Dev/Analyst I, Fidelity National Information Services, Jacksonville, FL (FNIS acquired Certegy in 2005 and out of 20 personal, was one of three kept on.) August 2003 to February 2005: Senior NetOps Operator, Certegy, St.Pete, Fl. (August 2003, Certegy terminated contract with EDS and out of 40 personal, was one of six kept on.) Projects: Creation and update of listing and placement for all raised floor equipment at St.Pete site. Listing was made up of, floor plan of the raised floor and equipment racks diagrams showing the placement of all devices using Visio. This was cross-referenced with an inventory excel document showing what dept was responsible for each device. Sole creator of Network operation and Server Operation procedures guide (NetOps Guide).  Expertise: Resolving circuit and/or router issues or assist circuit carrier in resolving issue from the company Network Operation Center (NOC). As well as resolving application problems or assist application support in resolution of it.     July 1999 to August 2003: Senior NetOps Operator,EDS (Certegy Account), St.Pete, FL Same expertise and on going projects as listed above for FNIS/Certegy. (Equifax outsourced the NetOps dept. to EDS in 1999)         January 1991 to July 1999: NetOps/Tandem Operator, Equifax, St.Pete & Tampa, FL Same as all of the above for FNIS/Certegy/EDS except for circuit and router issues   EDUCATION ? New Horizons Computer Learning Center, Jacksonville, Florida - CompTIA A+, Security+, and     Network+ Certified.                        Currently working on CCNA Certification 07/30/10 ? Mott Community College, Flint, Michigan – Associates Degree - Data Processing and General Education ? Currently studying Japanese

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• asynchrony is viral

  - by Daniel Moth

  It is becoming hard to write code today without introducing some form of asynchrony and, if you are using .NET (e.g. for Windows Phone 8 or Windows Store apps), that means sooner or later you have to await something and mark your method as async. My most recent examples included introducing speech recognition in my Translator By Moth phone app where I had to await mySpeechRecognizerUI.RecognizeWithUIAsync() and when moving that code base to a Windows Store project just to show a MessageBox I had to await myMessageDialog.ShowAsync(). Any time you need to invoke an asynchronous method in your code, you have a choice to make: kick off the operation but don’t wait for it to complete (otherwise known as fire-and-forget), synchronously wait for it to complete (which will entail blocking, which can be bad, especially on a UI thread), or asynchronously wait for it to complete before continuing on with the rest of the method’s work. In most cases, you want the latter, and the await keyword makes that trivial to implement.  When you use the magical await keyword in front of an API call, then you typically have to make additional changes to your code: This await usage is within a method of course, and now you have to annotate that method with async. Furthermore, you have to change the return type of the method you just annotated so it returns a Task (if it previously returned void), or Task<myOldReturnType> (if it previously returned myOldReturnType). Note that if it returns void, in some cases you could cheat and stop there. Furthermore, any method that called this method you just annotated with async will now also be invoking an asynchronous operation, so you have to make that change in the body of the caller method to introduce the await keyword before the call to the method. …you guessed it, you now have to change this caller method to be annotated with async and have its return types tweaked... …and it goes on virally… At some point you reach the root of your user code, e.g. a GUI event handler, and whoever calls that void method can already deal with the fact that you marked it as async and the viral introduction of the keywords stops there… This is all wonderful progress and a very powerful mechanism, and I just wish someone had written a refactoring tool to take care of this… anyone? I mentioned earlier that you have a choice when invoking an asynchronous operation. If the first time you encounter this you wish to localize the impact of all these changes and essentially try to turn the asynchronous behavior into synchronous by blocking - don't! For reasons why you don't want to do that, read Toub's excellent blog post (and check out the rest of his blog with gems on async programming starting with the Async FAQ). Just embrace the pattern knowing that when you use one instance of an await, you'll propagate the change all the way to the root user code method, e.g. typically an event handler. Related aside: I just finished re-writing my MessageBox wrapper class for Phone projects, including making it work in Windows Store projects, and it does expect you to use it with an await :-). I'll share that in an upcoming post for those of you that have the same need… Comments about this post by Daniel Moth welcome at the original blog.

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• SEO non-English domain name advice

  - by Dominykas Mostauskis

  I'm starting a website, that is meant for a non-English region, using an alphabet that is a bit different than that of English. Current plan is as follows. The website name, and the domain name, will be in the local language (not English); however, domain name will be spelled in the English alphabet, while the website's title will be the same word(s), but spelled properly with accents. E.g.: 'www.litterat.fr' and 'Littérat'. Does the difference between domain name and website name character use influence the site's SEO? Is it better, SEO-wise, to choose a name that can be spelled the same way in the English alphabet? From my experience, when searching online, invariably, the English alphabet is used, no matter the language, so people will still be searching 'litterat' (without accents and such). Edit: To sum up: Things have been said about IDN (Internationalized domain name). To make it simple, they are second-level domain names that contain language specific characters (LSP)(e.g. www.café.fr). Here you can check what top-level domains support what LSPs. Check initall's answer for more info on using LSPs in paths and queries. To answer my question about how and if search engines relate keywords spelled with and without language specific characters: Google can potentially tell that series and séries is the same keyword. However, (most relevant for words that are spelled differently across languages and have different meanings, like séries), for Google to make the connection (or lack thereof) between e and é, it has to deduce two things: Language that you are searching in. Language of your query. You can specify it manually through Advanced search or it guesses it, sometimes. I presume it can guess it wrong too. The more keywords specific to this language you use the higher Google's chance to guess the language. Language of the crawled document, against which the ASCII version of the word will be compared (in this example – series). Again, check initall's answer for how to help Google in understanding what language your document is in. Once it has that it can tell whether or not these two spellings should be treated as the same keyword. Google has to understand that even though you're not using french (in this example) specific characters, you're searching in French. The reason why I used the french word séries in this example, is that it demonstrates this very well. You have it in French and you have it in English without the accent. So if your search query is ambiguous like our series, unless Google has something more to go on, it will presume that there's no correlation between your search and séries in French documents. If you augment your query to series romantiques (try it), Google will understand that you're searching in French and among your results you'll see séries as well. But this does not always work, you should test it out with your keywords first. For example, if you search series francaises, it will associate francaises with françaises, but it will not associate series with séries. It depends on the words. Note: worth stressing that this problem is very relevant to words that, written in plain ASCII, might have some other meanings in other languages, it is less relevant to words that can be, by a distinct margin, just some one language. Tip: I've noticed that sometimes even if my non-accented search query doesn't get associated with the properly spelled word in a document (especially if it's the title or an important keyword in the doc), it still comes up. I followed the link, did a Ctrl-F search for my non-accented search query and found nothing, then checked the meta-tags in the source and you had the page's title in both accented and non-accented forms. So if you have meta-tags that can be spelled with language specific characters and without, put in both. Footnote: I hope this helps. If you have anything to add or correct, go ahead.

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• SQL SERVER – A Puzzle Part 4 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value

  - by pinaldave

  It seems like every weekend I get a new puzzle in my mind. Before continuing I suggest you read my previous posts here where I have shared earlier puzzles. A Puzzle – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value  A Puzzle Part 2 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value A Puzzle Part 3 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value After reading above three posts, I am very confident that you all will be ready for the next set of puzzles now. First execute the script which I have written here. Now guess what will be the next value as requested in the query. USE TempDB GO -- Create sequence CREATE SEQUENCE dbo.SequenceID AS DECIMAL(3,0) START WITH 1 INCREMENT BY -1 MINVALUE 1 MAXVALUE 3 CYCLE NO CACHE; GO SELECT next value FOR dbo.SequenceID; -- Guess the number SELECT next value FOR dbo.SequenceID; -- Clean up DROP SEQUENCE dbo.SequenceID; GO Please note that Starting value is 1, Increment value is the negative value of -1 and Minimum value is 3. Now let us first assume how this will work out. In our example of the sequence starting value is equal to 1 and decrement value is -1, this means the value should decrement from 1 to 0. However, the minimum value is 1. This means the value cannot further decrement at all. What will happen here? The natural assumption is that it should throw an error. How many of you are assuming about query will throw an ERROR? Well, you are WRONG! Do not blame yourself, it is my fault as I have told you only half of the story. Now if you have voted for error, let us continue running above code in SQL Server Management Studio. The above script will give the following output: Isn’t it interesting that instead of error out it is giving us result value 3. To understand the answer about the same, carefully observe the original syntax of creating SEQUENCE – there is a keyword CYCLE. This keyword cycles the values between the minimum and maximum value and when one of the range is exhausted it cycles the values from the other end of the cycle. As we have negative incremental value when query reaches to the minimum value or lower end it will cycle it from the maximum value. Here the maximum value is 3 so the next logical value is 3. If your business requirement is such that if sequence reaches the maximum or minimum value, it should throw an error, you should not use the keyword cycle, and it will behave as discussed. I hope, you are enjoying the puzzles as much as I am enjoying it. If you have any interesting puzzle to share, please do share with me and I will share this on blog with due credit to you. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• Hidden Features of C#?

  - by Serhat Özgel

  This came to my mind after I learned the following from this question: where T : struct We, C# developers, all know the basics of C#. I mean declarations, conditionals, loops, operators, etc. Some of us even mastered the stuff like Generics, anonymous types, lambdas, linq, ... But what are the most hidden features or tricks of C# that even C# fans, addicts, experts barely know? Here are the revealed features so far: Keywords yield by Michael Stum var by Michael Stum using() statement by kokos readonly by kokos as by Mike Stone as / is by Ed Swangren as / is (improved) by Rocketpants default by deathofrats global:: by pzycoman using() blocks by AlexCuse volatile by Jakub Šturc extern alias by Jakub Šturc Attributes DefaultValueAttribute by Michael Stum ObsoleteAttribute by DannySmurf DebuggerDisplayAttribute by Stu DebuggerBrowsable and DebuggerStepThrough by bdukes ThreadStaticAttribute by marxidad FlagsAttribute by Martin Clarke ConditionalAttribute by AndrewBurns Syntax ?? operator by kokos number flaggings by Nick Berardi where T:new by Lars Mæhlum implicit generics by Keith one-parameter lambdas by Keith auto properties by Keith namespace aliases by Keith verbatim string literals with @ by Patrick enum values by lfoust @variablenames by marxidad event operators by marxidad format string brackets by Portman property accessor accessibility modifiers by xanadont ternary operator (?:) by JasonS checked and unchecked operators by Binoj Antony implicit and explicit operators by Flory Language Features Nullable types by Brad Barker Currying by Brian Leahy anonymous types by Keith __makeref __reftype __refvalue by Judah Himango object initializers by lomaxx format strings by David in Dakota Extension Methods by marxidad partial methods by Jon Erickson preprocessor directives by John Asbeck DEBUG pre-processor directive by Robert Durgin operator overloading by SefBkn type inferrence by chakrit boolean operators taken to next level by Rob Gough pass value-type variable as interface without boxing by Roman Boiko programmatically determine declared variable type by Roman Boiko Static Constructors by Chris Easier-on-the-eyes / condensed ORM-mapping using LINQ by roosteronacid Visual Studio Features select block of text in editor by Himadri snippets by DannySmurf Framework TransactionScope by KiwiBastard DependantTransaction by KiwiBastard Nullable<T> by IainMH Mutex by Diago System.IO.Path by ageektrapped WeakReference by Juan Manuel Methods and Properties String.IsNullOrEmpty() method by KiwiBastard List.ForEach() method by KiwiBastard BeginInvoke(), EndInvoke() methods by Will Dean Nullable<T>.HasValue and Nullable<T>.Value properties by Rismo GetValueOrDefault method by John Sheehan Tips & Tricks nice method for event handlers by Andreas H.R. Nilsson uppercase comparisons by John access anonymous types without reflection by dp a quick way to lazily instantiate collection properties by Will JavaScript-like anonymous inline-functions by roosteronacid Other netmodules by kokos LINQBridge by Duncan Smart Parallel Extensions by Joel Coehoorn

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• NSURLErrorBadURL error

  - by Victor jiang

  My iphone app called Google Local Search(non javascript version) to behave some search business. Below is my code to form a url: NSString *url = [NSString stringWithFormat:@"http://ajax.googleapis.com/ajax/services/search/local?v=1.0&q=%@", keyword]; NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease]; [request setURL:[NSURL URLWithString:url]]; [request setHTTPMethod:@"GET"]; //get response NSHTTPURLResponse* urlResponse = nil; NSError *error = [[[NSError alloc] init] autorelease]; NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error:&error]; NSString *result = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding]; When the keyword refers to english characters, it works fine, but when refers to chinese characters(encoded in UTF8, such as '???' whose UTF8 code is 'e5a4a9 e5ae89 e997a8'), it will report NSURLErrorBadURL error(-1000, Returned when a URL is sufficiently malformed that a URL request cannot be initiated). Why? Then I carry out further investigation, I use Safari and type in the url below: http://ajax.googleapis.com/ajax/services/search/local?v=1.0&q=??? It also works, and the output I got from Macsniffer is: /ajax/services/search/local?v=1.0&q=%E5%A4%A9%E5%AE%89%E9%97%A8 So I write a testing url directly in my app NSString *url = [NSString stringWithFormat:@"http://ajax.googleapis.com/ajax/services/search/local?v=1.0&q=%E5%A4%A9%E5%AE%89%E9%97%A8"]; And what I got from the Macsniffer is some other thing: /ajax/services/search/local?v=1.0&q=1.687891E-28750X1.417C0001416CP-102640X1.4CC2D04648FBP-9999-1.989891E+0050X1.20DC00184CC67P-953E8E99A8 It seems my keyword "%E5%A4%A9%E5%AE%89%E9%97%A8" was translated into something else. So how can I form a valid url? I do need help!

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• Error C2451: Illegal conditional expression of type 'UnaryOp<E1, Op>' in ostream - visual studio 9

  - by Steven Hill

  I am getting a repeated error with VS 9. The code compiles under GNU C++, but I want debug with the VS IDE. Any idea what could be causing this error. Error 13 error C2451: conditional expression of type 'UnaryOp' is illegal \Microsoft Visual Studio 9.0\VC\include\ostream 512 //unary constraint template class UnaryOp : public Constraint { public: const E1& e1; UnaryOp(const E1& _e1); bool Satisfiable() const; Bool SatisfiableAux() const; void Print (std::ostream& os) const; UnaryOp* clone () const; //operator bool () const { return true; } }; template std::ostream& operator<<(std::ostream& os, const UnaryOp& unop); UnaryOp code that uses ostream: template INLINE void UnaryOp::Print (std::ostream& os) const { os << *this; } template INLINE std::ostream& operator<<(std::ostream& os, const UnaryOp& unop) { return os << Op::name << unop.e1; } ostream line with error: _Myt& __CLR_OR_THIS_CALL put(_Elem _Ch) { // insert a character ios_base::iostate _State = ios_base::goodbit; const sentry _Ok(*this); 512 if (!_Ok) _State |= ios_base::badbit; else { // state okay, insert character _TRY_IO_BEGIN

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• Finding string in php

  - by Roshan

  I have a content and i want to search a keyword in that content. Content When charting multiple data series, or just to improve the appearance of your charts, you can control the fill for each series in the chart or each item in a series. The fill lets you specify a pattern that defines how Flex draws the chart element. You also use fills to specify the background colors of the chart or bands of background colors defined by the grid lines. Fills can be solid or can use linear and radial gradients. A gradient specifies a gradual color transition in the fill color therefore. NOw, if the keyword we are searching is "When", it is the starting word so should display as "When charting multiple data ..........." If the keyword is "draws" , it lies in middle so should be displayed as ".... how Flex draws....." If the kewyword is "therefore", it is in the last position so should be displayed as ".........transition in the fill color therefore." Can anyone help me out how to do this in php server script?

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• Boost bind with asio::placeholders::error

  - by Leandro

  Why it doesn't work? --- boost_bind.cc --- #include #include #include void func1 (const int& i) { } void func2 (const ::asio::error_code& e) { } int main () { ::boost::function f1 = ::boost::bind (&func1, 1); // it doesn't work! ::boost::function f2 = ::boost::bind (&func2, ::asio::placeholders::error); return 0; } This is the error: while_true@localhost:~ g++ -lpthread boost_bind.cc -o boost_bind In file included from boost_bind.cc:2: /usr/include/boost/bind.hpp: In member function ‘void boost::_bi::list1::operator()(boost::_bi::type, F&, A&, int) [with F = void (*)(const asio::error_code&), A = boost::_bi::list0, A1 = boost::arg (*)()]’: /usr/include/boost/bind/bind_template.hpp:20: instantiated from ‘typename boost::_bi::result_traits::type boost::_bi::bind_t::operator()() [with R = void, F = void (*)(const asio::error_code&), L = boost::_bi::list1 (*)()]’ /usr/include/boost/function/function_template.hpp:152: instantiated from ‘static void boost::detail::function::void_function_obj_invoker0::invoke(boost::detail::function::function_buffer&) [with FunctionObj = boost::_bi::bind_t (*)() , R = void]’ /usr/include/boost/function/function_template.hpp:904: instantiated from ‘void boost::function0::assign_to(Functor) [with Functor = boost::_bi::bind_t (*)() , R = void]’ /usr/include/boost/function/function_template.hpp:720: instantiated from ‘boost::function0::function0(Functor, typename boost::enable_if_c::type) [with Functor = boost::_bi::bind_t (*)() , R = void]’ /usr/include/boost/function/function_template.hpp:1040: instantiated from ‘boost::function::function(Functor, typename boost::enable_if_c::type) [with Functor = boost::_bi::bind_t (*)() , R = void]’ boost_bind.cc:14: instantiated from here /usr/include/boost/bind.hpp:232: error: no match for ‘operator[]’ in ‘a[boost::_bi::storage1 (*)()::a1_ [with int I = 1]]’ while_true@localhost:~

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• Java: volatile guarantees and out-of-order execution

  - by WizardOfOdds

  Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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• Has Twisted changed its dependencies?

  - by cdecker

  Hi all, I'm currently working on a Python/Twisted project which is to be distributed and tested on Planetlab. For some reason my code was working on friday and now that I wanted to test a minor change it refuses to work at all: Traceback (most recent call last): File "acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/__init__.py", line 18, in <module> from twisted.python import compat File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/compat.py", line 146, in <module> import operator File "/home/cdecker/dev/acn/acn_a4/src/operator.py", line 7, in <module> File "/home/cdecker/acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/internet/protocol.py", line 20, in <module> from twisted.python import log, failure, components File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/log.py", line 19, in <module> from twisted.python import util, context, reflect File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/util.py", line 5, in <module> import os, sys, hmac, errno, new, inspect, warnings File "/usr/lib/python2.5/inspect.py", line 32, in <module> from operator import attrgetter ImportError: cannot import name attrgetter And since I'm pretty new to python I have no idea what could have caused this problem. All suggestions are welcome :-)

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• Question about functional OOP style in JavaScript

  - by valums

  I prefer to use functional OOP style for my code (similar to the module pattern) because it helps me to avoid the "new" keyword and all problems with the scope of "this" keyword in callbacks. But I've run into a few minor issues with it. I would like to use the following code to create a class. namespace.myClass = function(){ var self = {}, somePrivateVar1; // initialization code that would call // private or public methods privateMethod(); self.publicMethod(); // sorry, error here function privateMethod(){} self.publicMethod = function(){}; return self; } The problem is that I can't call public methods from my initialization code, as these functions are not defined yet. The obvious solution would be to create an init method, and call it before "return self" line. But maybe you know a more elegant solution? Also, how do you usually handle inheritance with this pattern? I use the following code, butI would like to hear your ideas and suggestions. namespace.myClass2 = function(){ var self = namespace.parentClass(), somePrivateVar1; var superMethod = self.someMethod; self.someMethod = function(){ // example shows how to overwrite parent methods superMethod(); }; return self; } Edit. For those who asked what are the reasons for choosing this style of OOP, you can look into following questions: http://stackoverflow.com/questions/1557386/prototypal-vs-functional-oop-in-javascript http://stackoverflow.com/questions/383402/is-javascript-s-new-keyword-considered-harmful

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• NSPredicate case-insensitive matching on to-many relationship

  - by Brian Webster

  I am implementing a search field where the user can type in a string to filter the items displayed in a view. Each object being displayed has a keywords to-many relationship, and I would like to be able to filter the objects based on their keywords. Each keyword object has a name property, so I've set up an NSPredicate to do the filtering that looks like this: NSPredicate* predicate = [NSPredicate predicateWithFormat:@"keywords.name CONTAINS %@", self.searchString]; This works, but the problem is that the search is case-sensitive, so if the keyword has a capital letter but the user types in all lowercase, no matches are found. I've tried the following modification: NSPredicate* predicate = [NSPredicate predicateWithFormat:@"keywords.name CONTAINS[c] %@", self.searchString]; But that doesn't make any difference in the case sensitivity of the matching. Is there a way to do this case-insensitive matching using just a plain predicate? Or will I need to implement some sort of custom accessor on the keyword class, e.g. write a lowercaseName method and match against a lowercased version of the search string instead? Addendum: After further exploration, the workaround of adding a custom accessor works OK for manual use of NSPredicate, but does not work at all when using NSFetchRequest with Core Data, which only works when querying attributes defined in the Core Data model.

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• How to print a number with a space as thousand separator?

  - by dygi

  I've got a simple class Currency with overloaded operator<<. I don't know how can i separate the number with spaces every 3 digits, so it looks like: "1 234 567 ISK". #include <cstdlib> #include <iostream> using namespace std; class Currency { int val; char curr[4]; public: Currency(int _val, const char * _curr) { val = _val; strcpy(curr, _curr); } friend ostream & operator<< (ostream & out, const Currency & c); }; ostream & operator<< (ostream & out, const Currency & c) { out << c.val<< " " << c.curr; return out; } int main(int argc, char *argv[]) { Currency c(2354123, "ISK"); cout << c; } What interests me, is somehow the easiest solution for this particular situation.

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• what data structure should I use for hash lookup as well as binary search?

  - by zebraman

  I am working on a school homework. I have a list of names. I want to be able to perform binary search on these names (find all names between a lower and upper bound) for first name as well as last name, and perform keyword searches as well (this will be accomplished using hashing. For example, if I have the names Garfield Cat Snoopy Dog Captain Crunch Fat Cat then a binary search of first names (C,H) will return Captain Crunch, Fat Cat, and Garfield Cat. A binary search of last names (Cr,D) will return Captain Crunch. A keyword search of 'cat' will return Fat Cat and Garfield Cat. I understand binary search will only work on a sorted list, but since I am planning on searching two different criteria, I will have to sort the list by last name or first name depending on what I'm searching for. I feel like it will be too inefficient to have to resort the list each time I want to perform a new binary search. Would it just be better for me to set up and maintain two sorted lists (one for sorted by first name, one for sorted by last name)? Also, for hashing, will I have to set up a different table of names for that as well? I understand each keyword will hash to some value determined by a hash function, and this value (or key) is a table address where the corresponding names are stored. So I just want to know what would be the best way to solve this problem? Maintaining separate structures, or is there a way to efficiently do everything I want with just one data structure?

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