15. 使用 Include 防范

ifndef

在本例中，你并不需要 ifndef 语句，因为代码很简单。你只写了一个类，所以不可能多次包含另一个类。但是，用 ifndef 语句来编写包含警卫是个好习惯。

在本练习中，你需要使用 ifndef 语法在 matrix.h 文件中编写一个 Include 防范程序。

Start Quiz: 

#include <iostream>
#include <vector>
#include "matrix.h"

int main () {
    
    // TODO: Nothing to do here
    
    return 0;
}
#include "matrix.h"

Matrix::Matrix() {
    std::vector <std:: vector <float> > initial_grid (10, std::vector <float>(5, 0.5));
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();

}

Matrix::Matrix(std::vector <std:: vector <float> > initial_grid) {
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();
}

void Matrix::setGrid(std::vector< std::vector<float> > new_grid) {
    grid = new_grid;
    rows = new_grid.size();
    cols = new_grid[0].size();

}

std::vector< std::vector<float> > Matrix::getGrid() {
    return grid;
}

std::vector<float>::size_type Matrix::getRows() {
    return rows;
}

std::vector<float>::size_type Matrix::getCols() {
    return cols;
}

Matrix Matrix::matrix_transpose() {
    std::vector< std::vector<float> > new_grid;
    std::vector<float> row;

    for (int i = 0; i < cols; i++) {
        row.clear();

        for (int j = 0; j < rows; j++) {
            row.push_back(grid[j][i]); 
        }
        new_grid.push_back(row);
    }

    return Matrix(new_grid);
}

Matrix Matrix::matrix_addition(Matrix other) {

    if ((rows != other.getRows()) || (cols != other.getCols())) {
        throw std::invalid_argument( "matrices are not the same size" );
    }

    std::vector< std::vector<float> > othergrid = other.getGrid();

    std::vector< std::vector<float> > result;

    std::vector<float> new_row;

    for (int i = 0; i < rows; i++) {
        new_row.clear();
        for (int j = 0; j < cols; j++) {
            new_row.push_back(grid[i][j] + othergrid[i][j]);
        }
        result.push_back(new_row);
    }

    return Matrix(result);
}

void Matrix::matrix_print() {

    std::cout << std::endl;

    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < cols; j++)
        {
            std::cout << grid[i][j] << " ";
        }
        std::cout << std::endl;
    }
    std::cout << std::endl;
}

#include <vector>
#include <iostream>
#include <stdexcept>

class Matrix
{
    private:

        std::vector< std::vector<float> > grid;
        std::vector<float>::size_type rows;
        std::vector<float>::size_type cols;

    public:

        // constructor functions
        Matrix ();
        Matrix (std::vector< std::vector<float> >);

        // set functions
        void setGrid(std::vector< std::vector<float> >);

        // get functions
        std::vector< std::vector<float> > getGrid();
        std::vector<float>::size_type getRows();
        std::vector<float>::size_type getCols();

        // matrix functions
        Matrix matrix_transpose();
        Matrix matrix_addition(Matrix);

        // matrix printing
        void matrix_print();

};

matrix.h 参考答案 

# ifndef MATRIX_H
# define MATRIX_H

# include <vector>
# include <iostream>
# include <stdexcept>

# include <vector>

class Matrix
{
    private:

        std::vector< std::vector<float> > grid;
        std::vector<int>::size_type rows;
        std::vector<int>::size_type cols;

    public:

        //构造函数
        Matrix ();
        Matrix (std::vector< std::vector<float> >);

        // set 函数
        void setGrid(std::vector< std::vector<float> >);

        // get 函数
        std::vector< std::vector<float> > getGrid();
        std::vector<int>::size_type getRows();
        std::vector<int>::size_type getCols();

        // matrix functions
        Matrix matrix_tranpose();
        Matrix matrix_addition(Matrix);

        // matrix printing
        void matrix_print();

};

# endif /* MATRIX_H */

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