- Joined
- 11/14/06
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- Points
- 16
Here's another approach to the problem of how to efficiently input a matrix to your code. This follows on from the thread on the LA refresher forum. This allows you to do the cut and paste thing like Barney sugggested, or to input the data from a file (suitably-named to avoid confusion down the line).
There's nothing wrong with the approaches suggested on the other thread, this is just an alternative that uses the I/O streams in the C++ standard libary a little differently.
One irritating thing here is that if using the console to input the values, you have to type Ctrl-Z as the last line of your input to indicate EOF to the C++ library code. Not sure how to get around that, but I only used this mode for testing anyway. This code is also brittle as heck but works OK with the inputs from Dan.
The matrix code I am using is in Boost::numerics::ublas (sorry Eddie), hence the use of templates e.g. matrix<double>.
Here's the actual reader code:
There's nothing wrong with the approaches suggested on the other thread, this is just an alternative that uses the I/O streams in the C++ standard libary a little differently.
One irritating thing here is that if using the console to input the values, you have to type Ctrl-Z as the last line of your input to indicate EOF to the C++ library code. Not sure how to get around that, but I only used this mode for testing anyway. This code is also brittle as heck but works OK with the inputs from Dan.
The matrix code I am using is in Boost::numerics::ublas (sorry Eddie), hence the use of templates e.g. matrix<double>.
Code:
[SIZE=2]matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> data = readMatrix(cin); [/SIZE][SIZE=2][COLOR=#008000]// read from the console[/COLOR][/SIZE]
[SIZE=2]matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> A = readMatrix([/SIZE][SIZE=2][COLOR=#800000]"LARefresher\\hw2a.txt"[/COLOR][/SIZE][SIZE=2]); [/SIZE][SIZE=2][COLOR=#008000]// read from file[/COLOR][/SIZE]
Code:
[SIZE=2][COLOR=#008000]// Read matrix elements from an input stream. Assumes well-formed data, line by line,[/COLOR][/SIZE]
[SIZE=2][COLOR=#008000]// terminated by CtrlZ (if from screen) or EOF (if from file)[/COLOR][/SIZE]
[SIZE=2]matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> readMatrix(istream &data)[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]std::vector<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> rowValues;[/SIZE]
[SIZE=2]std::vector<std::vector<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> > rows;[/SIZE]
[SIZE=2][COLOR=#0000ff]while[/COLOR][/SIZE][SIZE=2] ([/SIZE][SIZE=2][COLOR=#0000ff]true[/COLOR][/SIZE][SIZE=2])[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2][COLOR=#0000ff]char[/COLOR][/SIZE][SIZE=2] line[256];[/SIZE]
[SIZE=2]data.getline(line, [/SIZE][SIZE=2][COLOR=#0000ff]sizeof[/COLOR][/SIZE][SIZE=2](line));[/SIZE]
[SIZE=2][COLOR=#0000ff]if[/COLOR][/SIZE][SIZE=2] (data.fail() || data.eof())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2][COLOR=#0000ff]break[/COLOR][/SIZE][SIZE=2];[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]istrstream doubles(line);[/SIZE]
[SIZE=2][COLOR=#0000ff]while[/COLOR][/SIZE][SIZE=2] (!doubles.fail() && !doubles.eof())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]ws(doubles);[/SIZE]
[SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2] element;[/SIZE]
[SIZE=2]doubles >> element;[/SIZE]
[SIZE=2][COLOR=#0000ff]if[/COLOR][/SIZE][SIZE=2] (doubles.fail())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]cerr << [/SIZE][SIZE=2][COLOR=#800000]"malformed input line ("[/COLOR][/SIZE][SIZE=2] << string(line) << [/SIZE][SIZE=2][COLOR=#800000]")"[/COLOR][/SIZE][SIZE=2] << endl;[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]rowValues.push_back(element);[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]rows.push_back(rowValues);[/SIZE]
[SIZE=2]rowValues.clear();[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2][COLOR=#008000]// Reset input stream state[/COLOR][/SIZE]
[SIZE=2]data.clear();[/SIZE]
[SIZE=2]matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> m(rows.size(), rows.front().size());[/SIZE]
[SIZE=2]std::vector<std::vector<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> >::const_iterator rowData = rows.begin();[/SIZE]
[SIZE=2]Dimension next(0);[/SIZE]
[SIZE=2][COLOR=#0000ff]while[/COLOR][/SIZE][SIZE=2] (rowData != rows.end())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]matrix_row<matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> > mri (row(m, next));[/SIZE]
[SIZE=2]std::vector<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]>::const_iterator nextData = rowData->begin();[/SIZE]
[SIZE=2]matrix_row<matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> >::iterator matrixData = mri.begin();[/SIZE]
[SIZE=2][COLOR=#0000ff]while[/COLOR][/SIZE][SIZE=2] (nextData != rowData->end())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]*matrixData = *nextData;[/SIZE]
[SIZE=2]++matrixData;[/SIZE]
[SIZE=2]++nextData;[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]++rowData;[/SIZE]
[SIZE=2]++next;[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]cout << m;[/SIZE]
[SIZE=2][COLOR=#0000ff]return[/COLOR][/SIZE][SIZE=2] m;[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]matrix<[/SIZE][SIZE=2][COLOR=#0000ff]double[/COLOR][/SIZE][SIZE=2]> readMatrix(string filename)[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]ifstream myFile;[/SIZE]
[SIZE=2]myFile.open(filename.c_str());[/SIZE]
[SIZE=2][COLOR=#0000ff]if[/COLOR][/SIZE][SIZE=2] (!myFile.fail())[/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2][COLOR=#0000ff]return[/COLOR][/SIZE][SIZE=2] readMatrix(myFile);[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2][COLOR=#0000ff]else[/COLOR][/SIZE]
[SIZE=2]{[/SIZE]
[SIZE=2]cerr << [/SIZE][SIZE=2][COLOR=#800000]"cannot open file: ("[/COLOR][/SIZE][SIZE=2] << filename << [/SIZE][SIZE=2][COLOR=#800000]")"[/COLOR][/SIZE][SIZE=2] << endl;[/SIZE]
[SIZE=2][COLOR=#0000ff]throw[/COLOR][/SIZE][SIZE=2][COLOR=#800000]"cannot open file"[/COLOR][/SIZE][SIZE=2];[/SIZE]
[SIZE=2]}[/SIZE]
[SIZE=2]}[/SIZE]
