mex cplusplus matlab::da​ta::RowMaj​orIterator

This is an example of iterating through a matrix in Matlab's default column-major setup

void operator()(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs)
{                
    const matlab::data::TypedArray<double> data = std::move(inputs[0]);
    for (auto it = data.begin(); it != data.end();)
    {
        std::cout << *it++ << " ";        
    }
}

How can I do the same to iterate row-major with a matlab::data::RowMajorIterator iterator?

Answer 1

[Madheswaran]

Hi @Markus Leuthold

You can use the row-major iterator by utilizing the RowMajor class as follows:

void operator()(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs)
{
    const matlab::data::TypedArray<double> data = std::move(inputs[0]);
    
    // Option 1: Using explicit iterators
    for (auto it = matlab::data::RowMajor::begin<double>(data); 
         it != matlab::data::RowMajor::end<double>(data);)
    {
        std::cout << *it++ << " ";
    }
    
    // Option 2: Using range-based for loop with writableElements
    auto range = matlab::data::RowMajor::writableElements<double>(data);
    for (const auto& elem : range) {
        // ... Your code ...
    }
}

Make sure to include "RowMajorIterator.hpp" in your header files, and add the appropriate include path when compiling:

mex yourfile.cpp -I"matlabroot/extern/include/MatlabDataArray"

replace 'matlabroot' with abosolute path of your 'matlabroot' in the above command.

For more information, refer to the following documentations:

1. https://mathworks.com/help/matlab/apiref/matlab.data.rowmajor.html
2. https://mathworks.com/help/matlab/ref/mex.html

Hope this helps!