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  • Esoteric C++ operators

    - by Neil G
    What is the purpose of the following esoteric C++ operators? Pointer to member ::* Bind pointer to member by pointer ->* Bind pointer to member by reference .* (reference)

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  • C++ domain specific embedded language operators

    - by aaa
    hi. In numerical oriented languages (Matlab, Fortran) range operator and semantics is very handy when working with multidimensional data. For example: A(i:j,k,:n) // represents two-dimensional slice B(i:j,0:n) of A at index k unfortunately C++ does not have range operator (:). of course it can be emulated using range/slice functor, but semantics is less clean than Matlab. I am prototyping matrix/tensor domain language in C++ and am wondering if there any options to reproduce range operator. I still would like to rely on C++/prprocessor framework exclusively. So far I have looked through boost wave which might be an suitable option. is there any other means to introduce new operators to C++ DSL?

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  • YouTube: Tips by Bitwise Courses on NetBeans

    - by Geertjan
    I really like the potential of YouTube in providing a platform for short info clips that take not much time to produce and about as much time to consume. Huw Collingbourne's Bitwise Courses channel is full of exactly this kind of YouTube clip. Several of his YouTube clips are about or make use of NetBeans. The related Twitter account is @bitwisecourses and the homepage is bitwisecourses.com. Here's a great example, the latest YouTube clip created by Bitwise Courses. Very clear and simple explanation, on a specific and narrow topic, and very short and sweet. And very useful! Didn't know about this feature myself. Direct link to the movie: https://www.youtube.com/watch?v=b0fKT_hFQpU Here's to more of these, they're wonderful. More such YouTube clips are needed, short and precise, on very specific topics. And I'm very happy to promote them, as you can see.

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  • Dynamically created operators

    - by Gero
    I created a program using dev-cpp and wxwidgets which solves a puzzle. The user must fill the operations blocks and the results blocks, and the program will solve it. Im solving it using bruteforce, i generate all non repeated 9 length number combinations using a recursive algorithm. It does it pretty fast. Up to here all is great! But the problem is when my program operates depending the character on the blocks. Its extremely slow (it never gets the answer), because of the chars comparation against +, -, *, etc. Im doing a CASE. Is there some way or some programming language wich allows dinamic creation of operators? So i can define the operator ROW1COL2 to be a +, and the same way to all other operations. I leave a screenshot of the app, so its easier to understand how the puzzle works. http://www.imageshare.web.id/images/9gg5cev8vyokp8rhlot9.png PD: The algorithm works, i tryed it with a trivial puzzle, and solved it in a second.

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  • What do these C operators mean?

    - by Melkhiah66
    I'm reading the book "Programming Challenges: The Programming Contest Training Manual" and are implementing a problem where I do not understand the use of operators c1 and the comparison if (n&1), someone could help me to know they mean? this is the example code #include <stdio.h> #define MAX_N 300 #define MAX_D 150 long cache[MAX_N/2][2]; void make_cache(int n,int d,int mode) { long tmp[MAX_D]; int i,count; for(i=0;i<MAX_D;i++) tmp[i]=0; tmp[0]=1;count=0; while(count<=n) { count++; for(i=(count&1);i<=d;i+=2) { if(i) tmp[i] = tmp[i-1] + tmp[i+1]; else if(!mode) tmp[0]=tmp[1]; else tmp[0]=0; } if((count&1)==(d&1)) cache[count>>1][mode]=tmp[d]; } } int main() { int n,d,i; long sum; while(1) { scanf("%d %d",&n,&d); if(n&1) sum=0; else if(d==1) sum=1; else if(n<(d<<1)) sum=0; else if(n==(d<<1)) sum=1; else { make_cache(n,d,0); make_cache(n,d,1); sum=0; for(i=0;i<=(n>>1);i++) sum+=cache[i][0]*cache[(n>>1)-i][1]; } printf("%ld\n",sum); } return 0; }

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  • How do the operators < and > work with pointers?

    - by Øystein
    Just for fun, I had a std::list of const char*, each element pointing to a null-terminated text string, and ran a std::list::sort() on it. As it happens, it sort of (no pun intended) did not sort the strings. Considering that it was working on pointers, that makes sense. According to the documentation of std::list::sort(), it (by default) uses the operator < between the elements to compare. Forgetting about the list for a moment, my actual question is: How do these (, <, =, <=) operators work on pointers in C++ and C? Do they simply compare the actual memory addresses? char* p1 = (char*) 0xDAB0BC47; char* p2 = (char*) 0xBABEC475; e.g. on a 32-bit, little-endian system, p1 p2 because 0xDAB0BC47 0xBABEC475? Testing seems to confirm this, but I thought it'd be good to put it on StackOverflow for future reference. C and C++ both do some weird things to pointers, so you never really know...

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  • How to define 2-bit numbers in C, if possible?

    - by Eddy
    For my university process I'm simulating a process called random sequential adsorption. One of the things I have to do involves randomly depositing squares (which cannot overlap) onto a lattice until there is no more room left, repeating the process several times in order to find the average 'jamming' coverage %. Basically I'm performing operations on a large array of integers, of which 3 possible values exist: 0, 1 and 2. The sites marked with '0' are empty, the sites marked with '1' are full. Initially the array is defined like this: int i, j; int n = 1000000000; int array[n][n]; for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { array[i][j] = 0; } } Say I want to deposit 5*5 squares randomly on the array (that cannot overlap), so that the squares are represented by '1's. This would be done by choosing the x and y coordinates randomly and then creating a 5*5 square of '1's with the topleft point of the square starting at that point. I would then mark sites near the square as '2's. These represent the sites that are unavailable since depositing a square at those sites would cause it to overlap an existing square. This process would continue until there is no more room left to deposit squares on the array (basically, no more '0's left on the array) Anyway, to the point. I would like to make this process as efficient as possible, by using bitwise operations. This would be easy if I didn't have to mark sites near the squares. I was wondering whether creating a 2-bit number would be possible, so that I can account for the sites marked with '2'. Sorry if this sounds really complicated, I just wanted to explain why I want to do this.

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  • PowerPivot, Parent/Child and Unary Operators

    - by AlbertoFerrari
    Following my last post about parent/child hierarchies in PowerPivot, I worked a bit more to implement a very useful feature of Parent/Child hierarchies in SSAS which is obviously missing in PowerPivot, i.e. unary operators. A unary operator is simply the aggregation function that needs to be used to aggregate values of children over their parent. Unary operators are very useful in accountings where you might have incomes and expenses in the same hierarchy and, at the total level, you want to subtract...(read more)

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  • Improving Comparison Operators and Window Functions

    It is dangerous to assume that your data is sound. SQL already has intrinsic ways to cope with missing, or unknown data in its comparison predicate operators, or Theta operators. Can SQL be more effective in the way it deals with data quality? Joe Celko describes how the SQL Standard could soon evolve to deal with data in ways that allow aggregation and windowing in cases where the data quality is less than perfect

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  • using LIKE with logical operators

    - by ryanthegecko
    i can't seem to figure out how to combine LIKE with an OR or AND: DELETE * FROM persons WHERE FirstName = 'Abe' AND LastName LIKE '%coln'; Looks like it should owrk to me but I get error 1064 (syntax0 Is there a correct way to do this?

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  • FitNesse/Slim String Operators

    - by grootjans
    Is it possible to express this in a Query Table in FitNesse with SLIM for .net: contains(data) startswith(data) endswith(data) I know from a previous question it was possible for FitNesse/Fit with cell handler loader. I'm looking for the equivalent in Slim.

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  • Reference-type conversion operators: asking for trouble?

    - by Ben
    When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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  • C++ assignment operators dynamic arrays

    - by user2905445
    First off i know the multiplying part is wrong but i have some questions about the code. 1. When i am overloading my operator+ i print out the matrix using cout << *this then right after i return *this and when i do a+b on matix a and matix b it doesnt give me the same thing this is very confusing. 2. When i make matrix c down in my main i cant use my default constructor for some reason because when i go to set it = using my assignment operator overloaded function it gives me an error saying "expression must be a modifiable value. although using my constructor that sets the row and column numbers is the same as my default constructor using (0,0). 3. My assignment operator= function uses a copy constructor to make a new matrix using the values on the right hand side of the equal sign and when i print out c it doesn't give me anything Any help would be great this is my hw for a algorithm class which i still need to do the algorithm for the multiplying matrices but i need to solve these issues first and im having a lot of trouble please help. //Programmer: Eric Oudin //Date: 10/21/2013 //Description: Working with matricies #include <iostream> using namespace std; class matrixType { public: friend ostream& operator<<(ostream&, const matrixType&); const matrixType& operator*(const matrixType&); matrixType& operator+(const matrixType&); matrixType& operator-(const matrixType&); const matrixType& operator=(const matrixType&); void fillMatrix(); matrixType(); matrixType(int, int); matrixType(const matrixType&); ~matrixType(); private: int **matrix; int rowSize; int columnSize; }; ostream& operator<< (ostream& osObject, const matrixType& matrix) { osObject << endl; for (int i=0;i<matrix.rowSize;i++) { for (int j=0;j<matrix.columnSize;j++) { osObject << matrix.matrix[i][j] <<", "; } osObject << endl; } return osObject; } const matrixType& matrixType::operator=(const matrixType& matrixRight) { matrixType temp(matrixRight); cout << temp; return temp; } const matrixType& matrixType::operator*(const matrixType& matrixRight) { matrixType temp(rowSize*matrixRight.columnSize, columnSize*matrixRight.rowSize); if(rowSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { temp.matrix[i][j] = matrix[i][j] * matrixRight.matrix[i][j]; } } } else { cout << "Cannot multiply matricies that have different size rows from the others columns." << endl; } return temp; } matrixType& matrixType::operator+(const matrixType& matrixRight) { if(rowSize == matrixRight.rowSize && columnSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { matrix[i][j] += matrixRight.matrix[i][j]; } } } else { cout << "Cannot add matricies that are different sizes." << endl; } cout << *this; return *this; } matrixType& matrixType::operator-(const matrixType& matrixRight) { matrixType temp(rowSize, columnSize); if(rowSize == matrixRight.rowSize && columnSize == matrixRight.columnSize) { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { matrix[i][j] -= matrixRight.matrix[i][j]; } } } else { cout << "Cannot subtract matricies that are different sizes." << endl; } return *this; } void matrixType::fillMatrix() { for (int i=0;i<rowSize;i++) { for (int j=0;j<columnSize;j++) { cout << "Enter the matix number at (" << i << "," << j << "):"; cin >> matrix[i][j]; } } } matrixType::matrixType() { rowSize=0; columnSize=0; matrix = new int*[rowSize]; for (int i=0; i < rowSize; i++) { matrix[i] = new int[columnSize]; } } matrixType::matrixType(int setRows, int setColumns) { rowSize=setRows; columnSize=setColumns; matrix = new int*[rowSize]; for (int i=0; i < rowSize; i++) { matrix[i] = new int[columnSize]; } } matrixType::matrixType(const matrixType& otherMatrix) { rowSize=otherMatrix.rowSize; columnSize=otherMatrix.columnSize; matrix = new int*[rowSize]; for (int i = 0; i < rowSize; i++) { for (int j = 0; j < columnSize; j++) { matrix[i]=new int[columnSize]; matrix[i][j]=otherMatrix.matrix[i][j]; } } } matrixType::~matrixType() { delete [] matrix; } int main() { matrixType a(2,2); matrixType b(2,2); matrixType c(0,0); cout << "fill matrix a:"<< endl;; a.fillMatrix(); cout << "fill matrix b:"<< endl;; b.fillMatrix(); cout << a; cout << b; c = a+b; cout <<"matrix a + matrix b =" << c; system("PAUSE"); return 0; }

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  • Search object array for matching possible multiple values using different comparison operators

    - by Sparkles
    I have a function to search an array of objects for a matching value using the eq operator, like so: sub find { my ( $self, %params ) = @_; my @entries = @{ $self->{_entries} }; if ( $params{filename} ) { @entries = grep { $_->filename eq $params{filename} } @entries; } if ( $params{date} ) { @entries = grep { $_->date eq $params{date} } @entries; } if ( $params{title} ) { @entries = grep { $_->title eq $params{title} } @entries; } .... I wanted to also be able to pass in a qr quoted variable to use in the comparison instead but the only way I can think of separating the comparisons is using an if/else block, like so: if (lc ref($params{whatever}) eq 'regexp') { #use =~ } else { #use eq } Is there a shorter way of doing it? Because of reasons beyond my control I'm using Perl 5.8.8 so I can't use the smart match operator. TIA

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  • Arithmetic operators and function calling in C

    - by Robert Dalton
    I'm not quite sure why I can't do double a = (float) my_Function(45) / 2048 / 2340 / 90; printf("%.4",a); // prints out 0.00 But instead I have to use one more variable as: double a = (float) my_Function(45); double b = (float) a / 2048 / 2340 / 90; printf("%.4",b); // prints out the correct value

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  • Class Assignment Operators

    - by Maxpm
    I made the following operator overloading test: #include <iostream> #include <string> using namespace std; class TestClass { string ClassName; public: TestClass(string Name) { ClassName = Name; cout << ClassName << " constructed." << endl; } ~TestClass() { cout << ClassName << " destructed." << endl; } void operator=(TestClass Other) { cout << ClassName << " in operator=" << endl; cout << "The address of the other class is " << &Other << "." << endl; } }; int main() { TestClass FirstInstance("FirstInstance"); TestClass SecondInstance("SecondInstance"); FirstInstance = SecondInstance; SecondInstance = FirstInstance; return 0; } The assignment operator behaves as-expected, outputting the address of the other class. Now, how would I actually assign something from the other class? For example, something like this: void operator=(TestClass Other) { ClassName = Other.ClassName; }

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  • == and === operators in php

    - by Lizard
    Lets say I have a variable that will always be a string. Now take the code below: if($myVar === "teststring") Note $myVar will always be a string, so my questions is Which is quicker/best, using === (Indentity) or the == (Equality)?

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  • Type casting Collections using Conversion Operators

    - by Vyas Bharghava
    The below code gives me User-defined conversion must convert to or from enclosing type, while snippet #2 doesn't... It seems that a user-defined conversion routine must convert to or from the class that contains the routine. What are my alternatives? Explicit operator as extension method? Anything else? public static explicit operator ObservableCollection<ViewModel>(ObservableCollection<Model> modelCollection) { var viewModelCollection = new ObservableCollection<ViewModel>(); foreach (var model in modelCollection) { viewModelCollection.Add(new ViewModel() { Model = model }); } return viewModelCollection; } Snippet #2 public static explicit operator ViewModel(Model model) { return new ViewModel() {Model = model}; } Thanks in advance!

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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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