Passing a matrix from one methot to another

[vRltwE]

Hi,

I call a method matrix = matrix_read(iFile, lines, cols); that will return a matrix.

There is a problem in the way I am making this call. Netbeans output:

main.cpp: In function 'double matrix_read(std::istream&, int, int)':
main.cpp:83: error: cannot convert 'double (*)[(((unsigned int)(((int)cols) - 1)) + 1u)]' to 'double' in return
main.cpp: In function 'int main(int, char**)':
main.cpp:100: error: incompatible types in assignment of 'double' to 'double [(((unsigned int)(((int)lines) - 1)) + 1u)][(((unsigned int)(((int)cols) - 1)) + 1u)]'

But I can not understandt what it means...

Did someone understant what I need to do for solving this?

#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <sstream>

using namespace std;
/*
 * 
 */

int matrix_lines(istream &iFile) {
// Método para obter o número linhas da matriz.
    iFile.clear();
    iFile.seekg(0);
    int lines = 0;
    string line;
    while(!iFile.eof()) {
        getline (iFile, line);
        lines++;
    }
    cout << "Número de linhas: " << lines-1 << endl;
    return lines-1;
}

int matrix_cols(istream &iFile) {
// Método para obter o número de colunas da matriz.
    iFile.clear();
    iFile.seekg(0);

    string line;
    double n;
    int cols = 0;

    getline (iFile, line);
//    cout << line << endl;

    stringstream is(line);
    n = 0;
    while (is >> n) {
//        cout << n << endl;
        cols++;
    }


//
    cout << "Número de colunas: " << cols << endl;
    return cols;
}

double matrix_read(istream &iFile, int lines, int cols) {
// Método para ler a matriz.
    double matrix[lines][cols];
    double value, valueOut;
    iFile.clear();
    iFile.seekg(0);
    
    for(int i = 0; i < lines; i++){
        for(int j = 0; j < cols; j++){
            valueOut = (iFile >> value,value);
            cout <<  valueOut  << " ";
            matrix[i][j] = valueOut;
//            cout << iFile.get() << " ";
            
        }
        cout << "\n";
    }

//    cout << "Now values in memory:" << endl;
//    for(int i = 0; i < lines; i++){
//        for(int j = 0; j < cols; j++){
//            cout <<  matrix[i][j]  << " ";
//        }
//        cout << "\n";
//    }
    return matrix;
}

int main(int argc, char** argv) {
    
    int lines,cols;
    ifstream iFile;
    iFile.open("/home/cristiano/matrix3.dat");

    if(!iFile) { // file couldn't be opened
        cerr << "Error: file could not be opened" << endl;
        exit(1);
    }

    cols = matrix_cols(iFile);
    lines = matrix_lines(iFile);
    double matrix[lines][cols];
    matrix = matrix_read(iFile, lines, cols);
//    cout << "oi: " << oi << endl;

    iFile.close();

    return (EXIT_SUCCESS);
}

[Bazzy]

You can't use assignment operator for arrays (line 92) and in your function you should return a double**, not a double.
Try with dynamic arrays or STL: http://www.cplusplus.com/forum/articles/7459/

[vRltwE]

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[vRltwE]

Hi,

how can I do to pass matrix from method matrix_read to main?

/* 
 * File:   main.cpp
 * Author: cristiano
 *
 * Created on April 22, 2009, 11:32 AM
 */

#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>

using namespace std;
/*
 * 
 */

int matrix_lines(istream &iFile) {
// Método para obter o número linhas da matriz.
    iFile.clear();
    iFile.seekg(0);
    int lines = 0;
    string line;
    while(!iFile.eof()) {
        getline (iFile, line);
        lines++;
    }
    cout << "Número de linhas: " << lines-1 << endl;
    return lines-1;
}

int matrix_cols(istream &iFile) {
// Método para obter o número de colunas da matriz.
    iFile.clear();
    iFile.seekg(0);

    string line;
    double n;
    int cols = 0;

    getline (iFile, line);
//    cout << line << endl;

    stringstream is(line);
    n = 0;
    while (is >> n) {
//        cout << n << endl;
        cols++;
    }


//
    cout << "Número de colunas: " << cols << endl;
    return cols;
}

double** matrix_read(istream &iFile, int lines, int cols) {
// Método para ler a matriz.

    vector<vector<double> > matrix;
    matrix.resize(cols);
    for(int i = 0; i < cols; i++)
        matrix[i].resize(lines);

    double value;
    iFile.clear();
    iFile.seekg(0);
    
    for(int i = 0; i < lines; i++){
        for(int j = 0; j < cols; j++){
           matrix[i][j]  = (iFile >> value,value);
           cout << matrix[i][j] << " ";
        }
        cout << "\n";
    }
    return matrix;
}

int main(int argc, char** argv) {
    
    int lines,cols;
    ifstream iFile;
    iFile.open("/home/cristiano/matrix3.dat");

    if(!iFile) { // file couldn't be opened
        cerr << "Error: file could not be opened" << endl;
        exit(1);
    }

    cols = matrix_cols(iFile);
    lines = matrix_lines(iFile);

//    vector<vector<double> > matrix;
//    matrix.resize(cols);
//    for(int i = 0; i < cols; i++)
//        matrix[i].resize(lines);

    matrix_read(iFile, lines, cols);


    iFile.close();

    return (EXIT_SUCCESS);
}