How to call mexCallMATLAB on a function that has inputs of different types?

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Robert 2013-6-20

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I would like to call the following function from a mex file:

norm(X, 'fro')

X is a double matrix. 'fro' is obviously a character array. How would I construct an input array, such to be able to use mexCallMATLAB, i.e.:

mexCallMATLAB(1, normOutputs, 2, normInputs, "norm")

Since the inputs have different types (mxArray and character array), I'm not sure how to construct an array of pointers to them. Help would be greatly appreciated!

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Answer 1

James Tursa 2013-6-20

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编辑：James Tursa 2013-6-20

在 MATLAB Online 中打开

mxArray *normInputs[2];
mxArray *normOutputs[1];
normInputs[0] = mxCreateDoubleMatrix(2,2,mxREAL); // a double matrix
// code to fill in normInputs[0]
normInputs[1] = mxCreateString("fro");
mexCallMATLAB(1,normOutputs,2,normInputs,"norm");
mxDestroyArray(normInputs[1]);
mxDestroyArray(normInputs[0]);
// use normOutputs[0]
mxDestroyArray(normOutputs[0]);

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James Tursa 2013-6-20

编辑：James Tursa 2013-6-20

在 MATLAB Online 中打开

Hmmm ... I thought norm always returned an answer. You can try this:

if( normOutputs[0] ) {
    mxDestroyArray(normOutputs[0]);
}

Or just remove the mxDestroyArray(normOutputs[0]) line completely and let the garbage collection handle it.

Neither of these answers is satisfactory to me, however, since to my understanding of the mexCallMATLAB call you should get a normOutputs[0] result. Don't know why this would not be the case. Are you sure you haven't already called mxDestroyArray(normOutputs[0]) prior to this line?

Robert 2013-6-20

编辑：Robert 2013-6-20

I figured out the problem! I am running this code in a loop, and the problem actually occurred the second time mxDestroyArray(normOutputs[0]) was called. So, if I put this line outside of the loop, the error goes away.

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Answer 2

Jan 2013-6-20

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https://ww2.mathworks.cn/matlabcentral/answers/79648-how-to-call-mexcallmatlab-on-a-function-that-has-inputs-of-different-types#answer_89385

编辑：Jan 2013-6-20

在 MATLAB Online 中打开

No, the inputs do not have different types and 'fro' is not a char vector, although it looks like it is one. Both variables must be mxArrays to be valid input arguments for mxCallMATLAB. So the 2nd normInput must be an mxArray pointer of the type mxCHAR (as shonw in James' example already):

normInput[1] = mxCreateString('fro');