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  • A mysterious compilation error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>'

    - by Stephane Rolland
    I wanted to protect the access to a log file that I use for multithreaded logging with boostlog library. I tried this stream class class ThreadSafeStream { public: template <typename TInput> const ThreadSafeStream& operator<< (const TInput &tInput) const { // some thread safe file access return *this; } }; using it this way (text_sink is a boostlog object): //... m_spSink.reset(new text_sink); text_sink::locked_backend_ptr pBackend = m_spSink->locked_backend(); const boost::shared_ptr< ThreadSafeStream >& spFileStream = boost::make_shared<ThreadSafeStream>(); pBackend->add_stream(spFileStream); // this causes the compilation error and I get this mysterious error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' the whole compile error: Log.cpp(79): error C2664: 'boost::log2_mt_nt5::sinks::basic_text_ostream_backend<CharT>::add_stream' : cannot convert parameter 1 from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T> &' 1> with 1> [ 1> CharT=char 1> ] 1> and 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> Reason: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' 1> with 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called I suspect that I am not well defining the operator<<()... but I don't find what is wrong.

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  • Memory not being freed, causing giant memory leak

    - by Delan Azabani
    In my Unicode library for C++, the ustring class has operator= functions set for char* values and other ustring values. When doing the simple memory leak test: #include <cstdio> #include "ucpp" main() { ustring a; for(;;)a="MEMORY"; } the memory used by the program grows uncontrollably (characteristic of a program with a big memory leak) even though I've added free() calls to both of the functions. I am unsure why this is ineffective (am I missing free() calls in other places?) This is the current library code: #include <cstdlib> #include <cstring> class ustring { int * values; long len; public: long length() { return len; } ustring() { len = 0; values = (int *) malloc(0); } ustring(const ustring &input) { len = input.len; values = (int *) malloc(sizeof(int) * len); for (long i = 0; i < len; i++) values[i] = input.values[i]; } ustring operator=(ustring input) { ustring result(input); free(values); len = input.len; values = input.values; return * this; } ustring(const char * input) { values = (int *) malloc(0); long s = 0; // s = number of parsed chars int a, b, c, d, contNeed = 0, cont = 0; for (long i = 0; input[i]; i++) if (input[i] < 0x80) { // ASCII, direct copy (00-7f) values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = input[i]; } else if (input[i] < 0xc0) { // this is a continuation (80-bf) if (cont == contNeed) { // no need for continuation, use U+fffd values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = 0xfffd; } cont = cont + 1; values[s - 1] = values[s - 1] | ((input[i] & 0x3f) << ((contNeed - cont) * 6)); if (cont == contNeed) cont = contNeed = 0; } else if (input[i] < 0xc2) { // invalid byte, use U+fffd (c0-c1) values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = 0xfffd; } else if (input[i] < 0xe0) { // start of 2-byte sequence (c2-df) contNeed = 1; values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = (input[i] & 0x1f) << 6; } else if (input[i] < 0xf0) { // start of 3-byte sequence (e0-ef) contNeed = 2; values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = (input[i] & 0x0f) << 12; } else if (input[i] < 0xf5) { // start of 4-byte sequence (f0-f4) contNeed = 3; values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = (input[i] & 0x07) << 18; } else { // restricted or invalid (f5-ff) values = (int *) realloc(values, sizeof(int) * ++s); values[s - 1] = 0xfffd; } len = s; } ustring operator=(const char * input) { ustring result(input); free(values); len = result.len; values = result.values; return * this; } ustring operator+(ustring input) { ustring result; result.len = len + input.len; result.values = (int *) malloc(sizeof(int) * result.len); for (long i = 0; i < len; i++) result.values[i] = values[i]; for (long i = 0; i < input.len; i++) result.values[i + len] = input.values[i]; return result; } ustring operator[](long index) { ustring result; result.len = 1; result.values = (int *) malloc(sizeof(int)); result.values[0] = values[index]; return result; } operator char * () { return this -> encode(); } char * encode() { char * r = (char *) malloc(0); long s = 0; for (long i = 0; i < len; i++) { if (values[i] < 0x80) r = (char *) realloc(r, s + 1), r[s + 0] = char(values[i]), s += 1; else if (values[i] < 0x800) r = (char *) realloc(r, s + 2), r[s + 0] = char(values[i] >> 6 | 0x60), r[s + 1] = char(values[i] & 0x3f | 0x80), s += 2; else if (values[i] < 0x10000) r = (char *) realloc(r, s + 3), r[s + 0] = char(values[i] >> 12 | 0xe0), r[s + 1] = char(values[i] >> 6 & 0x3f | 0x80), r[s + 2] = char(values[i] & 0x3f | 0x80), s += 3; else r = (char *) realloc(r, s + 4), r[s + 0] = char(values[i] >> 18 | 0xf0), r[s + 1] = char(values[i] >> 12 & 0x3f | 0x80), r[s + 2] = char(values[i] >> 6 & 0x3f | 0x80), r[s + 3] = char(values[i] & 0x3f | 0x80), s += 4; } return r; } };

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  • What does "===" mean?

    - by Stefan Konno
    I recently studied some code that I'm supposed to use for different reasons, it's unrelevant. The thing I've noticed is someone using the operator "===" which I can't make sense out of. I've tried it with a function and it corresponds in crazy ways. The language is PHP by the way. Does anyone know what the definition of this operator is, I can't even find it in the declaration of php operators.

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  • which is the most secure way to check variables type javascript

    - by mck89
    Hi, i need to check the type of a variable in javascript, i know 3 ways to do it: instanceof operator: if(a instanceof Function) typeof operator: if(typeof a=="function" toString method (jQuery uses this): Object.prototype.toString.call(a) == "[object Function]" Which is the most secure way to do type checking beetween these solutions? and why? Please don't tell me that the last solution is better only because jQuery uses that.

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  • Scheme define/lambda shorthand

    - by incrediman
    In Scheme, how can I make use of the define/lambda shorthand for nested lambda expressions within my define? For example given the following procedure... (define add (lambda (num1 num2) (+ num1 num2))) One can shorten it to this: (define (add num1 num2) (+ num1 num2)) However, how can I shorten the following function similarly ? (define makeOperator (lambda (operator) (lambda (num1 num2) (operator num1 num2)))) ;example useage - equivalent to (* 3 4): ((makeOperator *) 3 4)

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  • Why can't I add pointers

    - by Knowing me knowing you
    Having very similiar code like so: LINT_rep::Iterator::difference_type LINT_rep::Iterator::operator+(const Iterator& right)const { return (this + &right);//IN THIS PLACE I'M GETTING AN ERROR } LINT_rep::Iterator::difference_type LINT_rep::Iterator::operator-(const Iterator& right)const {//substracts one iterator from another return (this - &right);//HERE EVERYTHING IS FINE } err msg: Error 1 error C2110: '+' : cannot add two pointers Why I'm getting an err in one place and not in both?

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  • which is the most accurate way to check variables type javascript

    - by mck89
    Hi, i need to check the type of a variable in javascript, i know 3 ways to do it: instanceof operator: if(a instanceof Function) typeof operator: if(typeof a=="function" toString method (jQuery uses this): Object.prototype.toString.call(a) == "[object Function]" Which is the most accurate way to do type checking beetween these solutions? and why? Please don't tell me that the last solution is better only because jQuery uses that.

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  • What features would you like to see added to C++?

    - by George Edison
    Are there any features you would like to see added to C++? Maybe... A programming construct An extra operator A built-in function you think would be useful I realize questions like this are frowned upon, but I think this one is a genuine programming question that can be answered and the answers will spawn valuable discussion. (And it's community wiki.) Here is one of mine: How come C++ has no exponent operator, like Python's **?

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  • What features would you like to see added to your favorite programming language?

    - by George Edison
    Are there any features you would like to see added to a programming language? Maybe... A programming construct An extra operator A built-in function you think would be useful I realize questions like this are frowned upon, but I think this one is a genuine programming question that can be answered and the answers will spawn valuable discussion. (And it's community wiki.) Here is one of mine: How come C++ has no exponent operator, like Python's **?

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  • Deallocation doesn't free mem. in Windows/C++ Application

    - by Paul Baumer
    Hi, My Windows/C++ application allocates ~1Gb of data in memory with the new operator and processes this data. The data is deleted after processing. I noticed that if I run the processing again without exiting the application, the second call to "new" operator to allocate ~1gb of data fails. I would expect Windows to deliver back the memory again. Could this be managed in a better way with some other win32 calls etc. ? Thanks, Paul

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  • C++ adding friend to a template class in order to typecast

    - by user1835359
    I'm currently reading "Effective C++" and there is a chapter that contains code similiar to this: template <typename T> class Num { public: Num(int n) { ... } }; template <typename T> Num<T> operator*(const Num<T>& lhs, const Num<T>& rhs) { ... } Num<int> n = 5 * Num<int>(10); The book says that this won't work (and indeed it doesn't) because you can't expect the compiler to use implicit typecasting to specialize a template. As a soluting it is suggested to use the "friend" syntax to define the function inside the class. //It works template <typename T> class Num { public: Num(int n) { ... } friend Num operator*(const Num& lhs, const Num& rhs) { ... } }; Num<int> n = 5 * Num<int>(10); And the book suggests to use this friend-declaration thing whenever I need implicit conversion to a template class type. And it all seems to make sense. But why can't I get the same example working with a common function, not an operator? template <typename T> class Num { public: Num(int n) { ... } friend void doFoo(const Num& lhs) { ... } }; doFoo(5); This time the compiler complaints that he can't find any 'doFoo' at all. And if i declare the doFoo outside the class, i get the reasonable mismatched types error. Seems like the "friend ..." part is just being ignored. So is there a problem with my understanding? What is the difference between a function and an operator in this case?

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  • Dynamic Comparison Operators in PHP

    - by BenTheDesigner
    Hi All Is it possible, in any way, to pass comparison operators as variables to a function? I am looking at producing some convenience functions, for example (and I know this won't work): function isAnd($var, $value, $operator = '==') { if(isset($var) && $var $operator $value) return true; } if(isAnd(1, 1, '===')) echo 'worked'; Thanks in advance.

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  • Does string concatenation use StringBuilder internally?

    - by JamesBrownIsDead
    Three of my coworkers just told me that there's no reason to use a StringBuilder in place of concatenation using the + operator. In other words, this is fine to do with a bunch of strings: myString1 + myString2 + myString3 + myString4 + mySt... The rationale that they used was that since .NET 2, the C# compiler will build the same IL if you use the + operator as if you used a StringBuilder. This is news to me. Are they correct?

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  • references in C++

    - by Alexander
    Once I read in a statement that The language feature that "sealed the deal" to include references is operator overloading. Why are references needed to effectively support operator overloading?? Any good explanation?

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  • How do i cast an object to a string when object is not a string?

    - by acidzombie24
    I have class A, B, C. They all can implicitly convert to a string public static implicit operator A(string sz_) { ... return sz; } I have code that does this object AClassWhichImplicitlyConvertsToString { ... ((KnownType)(String)AClassWhichImplicitlyConvertsToString).KnownFunc() } The problem is, AClassWhichImplicitlyConvertsToString isnt a string even though it can be typecast into one implicitly. I get a bad cast exception. How do i say its ok as long as the class has an operator to convert into a string?

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  • C/C++ line number

    - by Betamoo
    In the sake of debugging purposes, can I get the line number in C/C++ compilers? (standard way or specific ways for certain compilers) e.g if(!Logical) printf("Not logical value at line number %d \n",LineNumber); // How to get LineNumber without writing it by my hand?(dynamic compilation) Thanks

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  • overloading new/delete problem

    - by hidayat
    This is my scenario, Im trying to overload new and delete globally. I have written my allocator class in a file called allocator.h. And what I am trying to achieve is that if a file is including this header file, my version of new and delete should be used. So in a header file "allocator.h" i have declared the two functions extern void* operator new(std::size_t size); extern void operator delete(void *p, std::size_t size); I the same header file I have a class that does all the allocator stuff, class SmallObjAllocator { ... }; I want to call this class from the new and delete functions and I would like the class to be static, so I have done this: template<unsigned dummy> struct My_SmallObjectAllocatorImpl { static SmallObjAllocator myAlloc; }; template<unsigned dummy> SmallObjAllocator My_SmallObjectAllocatorImpl<dummy>::myAlloc(DEFAULT_CHUNK_SIZE, MAX_OBJ_SIZE); typedef My_SmallObjectAllocatorImpl<0> My_SmallObjectAllocator; and in the cpp file it looks like this: allocator.cc void* operator new(std::size_t size) { std::cout << "using my new" << std::endl; if(size > MAX_OBJ_SIZE) return malloc(size); else return My_SmallObjectAllocator::myAlloc.allocate(size); } void operator delete(void *p, std::size_t size) { if(size > MAX_OBJ_SIZE) free(p); else My_SmallObjectAllocator::myAlloc.deallocate(p, size); } The problem is when I try to call the constructor for the class SmallObjAllocator which is a static object. For some reason the compiler are calling my overloaded function new when initializing it. So it then tries to use My_SmallObjectAllocator::myAlloc.deallocate(p, size); which is not defined so the program crashes. So why are the compiler calling new when I define a static object? and how can I solve it?

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  • string.format vs + for string concatenatoin

    - by AMissico
    Which is better in respect to performance and memory utilization? // + Operator oMessage.Subject = "Agreement, # " + sNumber + ", Name: " + sName; // String.Format oMessage.Subject = string.Format("Agreement, # {0}, Name: {1}", sNumber, sName); My preference is memory utilization. The + operator is used throughout the application. String.Format and StringBuilder is rarely use. I want to reduce the amount of memory fragmentation caused by excessive string allocations.

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  • Shift Operators in C++

    - by Codeguru
    If the value after the shift operator is greater than the number of bits in the left-hand operand, the result is undefined. If the left-hand operand is unsigned, the right shift is a logical shift so the upper bits will be filled with zeros. If the left-hand operand is signed, the right shift may or may not be a logical shift (that is, the behavior is undefined). Can somebody explain me what the above lines mean??

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  • c++ template and its element type

    - by David
    This is my template matrix class: template<typename T> class Matrix { public: .... Matrix<T> operator / (const T &num); } However, in my Pixel class, I didn't define the Pixel/Pixel operator at all! Why in this case, the compiler still compiles?

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  • C++: How to 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 m1.internal_field == m2.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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  • by reference in C++

    - by lego69
    I have this snippet of the code Stack& Stack:: operator=(const Stack& stack){ if(this == &stack){ return *this } } here I define operator = but I can't understand, if I receive by reference stack why it should be & in this == &stack and not this == stack and why we return * in return *this and not this thanks in advance for any help

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  • Lifting a math symbol in LaTeX

    - by Chris Conway
    I'm using the symbol \otimes as a unary operator and it's vertical alignment doesn't seem right to me. It wants to sit a bit below the baseline: and I tried using \raisebox to fix this, e.g., \raisebox{1pt}{$\otimes$}: But \raisebox doesn't seem to be sensitive to subscripts. The operator stays the same size while everything around it shrinks: The problem, I think, is that \raisebox creates its own LR box, which doesn't inherit the settings in the surrounding math environment. Is there a version of \raisebox that "respects math"?

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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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