stl

问题 The following code will print value of a and b: double a = 3.0, b=1231231231233.0123456; cout.setf(std::ios::fixed); cout.unsetf(std::ios::scientific); cout << a << endl << b << endl The output is: 3.000000 1231231231233.012451 You can see that a is outputed with fixed 6 count of decimals. But I want the output like this: 3 1231231231233.012451 How can i set flags only once, and output the above result. 回答1: The stream inserts 0 s following the double because the stream's default precision

问题 I have two vectors of floats and i want them to become one vector of Complex numbers. I'm stuck. I don't mind using iterators, but i am sure it'd be rediscovering the wheel i'm not informed about. Is my code leading me in the right direction? typedef std::vector<float> CVFloat; CVFloat vA, vB; //fil vectors typedef std::complex<CVFloat> myComplexVector; myComplexVector* vA_Complex = new myComplexVector(vA, vB); The code above is going through the compiler correctly, but when i want to get

问题 I've run into a very serious (IMO) problem. I am using the native cross platform tools in visual studio 2015. Since several implementations of the standard library were downloaded by visual studio C:\ProgramData\Microsoft\AndroidNDK\android-ndk-r10e\sources\cxx-stl\ I was surprised when I started finding stl classes that were not compiling. I wrote off std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> not being available as a quirk of gnu-libstdc++. I tried to set the stl to others to

问题 While i'm reading about STL iterators, this note found in https://www.sgi.com/tech/stl/Iterators.html The most restricted sorts of iterators are Input Iterators and Output Iterators, both of which permit "single pass" algorithms but do not necessarily support "multi-pass" algorithms. What does the mean of "Single Pass Algorithms" What does the mean of above sentence 回答1: Iinput-iterators are one-pass iterators i.e You can iterate over them only once. Whereas forward iterators are multi-pass.

问题 I'm using the STL allocator mentioned here. The only change I'm making is that I'm inheriting from a base class called Object, and I use base class' new and delete functions for allocation. class MyAlloc :public Object{ ...... } I want to use the parameterized constructor of the base class which will be based on parameter sent to the STLAllocator, which would be something like this. MyAlloc(A *a) : Object(a) { ... } And then use this constructor like : A *a = new A(); std::vector<int,MyAlloc

问题 I am trying to multiply two matrices in MPI but my both matrices are in vector form. vector <vector <int> > Mat1; Which in MxN order vector <vector <int> > Mat2; Which is NxL order and the results is also in vector form vector <vector <int> > Mat3; which is MxL order. I am using MPI_BCAST to broadcast the values as MPI_Bcast(Mat2.data(), Mat2.size(), MPI_INT, 0, MPI_COMM_WORLD); and using scatter and gather function to receive the data as MPI_Scatterv(Mat1.data(), CNTS, SNTS, MPI_INT,

问题 I am trying to multiply two matrices in MPI but my both matrices are in vector form. vector <vector <int> > Mat1; Which in MxN order vector <vector <int> > Mat2; Which is NxL order and the results is also in vector form vector <vector <int> > Mat3; which is MxL order. I am using MPI_BCAST to broadcast the values as MPI_Bcast(Mat2.data(), Mat2.size(), MPI_INT, 0, MPI_COMM_WORLD); and using scatter and gather function to receive the data as MPI_Scatterv(Mat1.data(), CNTS, SNTS, MPI_INT,

问题 bool pred(int k, int l, int num1, int num2) { return (num1 < num2); } int main() { vector <int> nums; for (int i=50; i > 0; --i) { nums.push_back(i); } std::sort (nums.begin(), nums.end(), boost::bind(&pred, 5, 45)); } I am a boost newbie. I was learning to use boost::bind and I wanted to sort a vector of integers and get rid of all those elements in the vector that are greater than 45 and less than 5. Had a hard time doing it. Would be great if anyone could help me do it? The reason I am

问题 First_Layer I have a win32 dll written in VC++6 service pack 6. Let's call this dll as FirstLayer. I do not have access to FirstLayer's source code but I need to call it from managed code. The problem is that FirstLayer makes heavy use of std::vector and std::string as function arguments and there is no way of marshaling these types into a C# application directly. Second_Layer The solution that I can think of is to first create another win32 dll written in VC++6 service pack 6. Let's call