Copy constructor and Co.

copyclass.cpp

#include <climits>
#include <iostream>
#include <cstring>
#include <new>

using namespace std;

class Matrix {
    double *nums;
    size_t nrows, ncols;
public:
    /// 1. Реализовать методы для получения и перезаписи строки и столбца из vector<double>.
    /// 2. Реализовать ленивое копирование (с подсчётом ссылок).
    Matrix(size_t nrows, size_t ncols) : nrows(nrows), ncols(ncols) {
        if (ncols >= SIZE_MAX / sizeof(double))
            throw out_of_range("too large columns count");
        nums = static_cast<double*>(calloc(nrows, ncols * sizeof(double)));
        if (!nums)
            throw bad_alloc();
    }
    Matrix(const Matrix &m) : nrows(m.nrows), ncols(m.ncols) {
        auto sz = nrows*ncols*sizeof(double);
        nums = static_cast<double*>(malloc(sz));
        if (!nums)
            throw bad_alloc();
        memcpy(nums, m.nums, sz);
    }
    ~Matrix() { cerr << "!destructor " << (intptr_t)nums << "!"; free(nums); }
    Matrix& operator=(const Matrix &m) {
        if (ncols != m.ncols || nrows != m.nrows)
            throw out_of_range("matricies do not have same bounds");
        memcpy(nums, m.nums, nrows*ncols*sizeof(double));
    }
    double& operator()(size_t row, size_t col) {
        cerr << '(' << (intptr_t)this << ')';
        if (row >= nrows)
            throw out_of_range("invalid row index");
        if (col >= ncols)
            throw out_of_range("invalid column index");
        return nums[row * ncols + col];
    }
    double operator()(size_t row, size_t col) const {
        cerr << '[' << (intptr_t)this << ']';
        if (row >= nrows)
            throw out_of_range("invalid row");
        if (col >= ncols)
            throw out_of_range("invalid column index");
        return nums[row * ncols + col];
    }
    Matrix operator*(double n) const {
        Matrix m(nrows, ncols);
        for (size_t row = 0; row < nrows; row++)
            for (size_t col = 0; col < ncols; col++)
                m(row, col) = (*this)(row, col) * n;
        return m;
    }
    friend ostream& operator<<(ostream &os, const Matrix &m);
};

 ostream& operator<<(ostream &os, const Matrix &m) {
    for (size_t row = 0; row < m.nrows; row++) {
        for (size_t col = 0; col < m.ncols; col++)
            os << m(row, col) << ' ';
        os << endl;
    }
    return os;
}

int main()
{
    Matrix m1(5, 5); m1(0, 0) = 1; m1(0, 1) = 2; m1(1, 0) = 3; m1(1, 1) = -0.5;
    cout << m1 << endl;
    Matrix m2 = m1 * -1.3;
    cout << m2 << endl;
    Matrix m3(5, 5);
    m3 = m2;
    cout << m3 << endl;
    return 0;
}