Unrecognized function or variable 'mexUnwrap'.

I get this error: “Unrecognized function or variable 'mexUnwrap'” when I run my code. However, the folder containing this C++ file (mexUnwrap.c) is in my path. It also contains mexUnwrap.mexa64, mexUnwrap.mexmaci64, mexUnwrap.mexw64. Do you have any suggestions for solving this problem?

[Steven Lord]

What does this command show when you run it on your machine? Do you have a file named mexUnwrap with that extension in the folder?

mexext

mexa64

If not, you'd need to build that MEX-file on that platform.

[Walter Roberson]

Perhaps @Pierre is using Apple Silicon and so needs to mex the code in order to generate a mexmaca64 file...

Answer 1

[Harsh]

Hi Pierre,

From what I can gather, you are unable to use the “mexUnwrap” function in MATLAB. To use functions or variables from C/C++ in MATLAB, please follow these steps:

1. Create your C/C++ file in the following format, ensuring you include “mex.h”:

#include "mex.h"

/* The gateway function */
void mexFunction(int nlhs, mxArray *plhs[],
                 int nrhs, const mxArray *prhs[]) {
    /* variable declarations */
    double num1, num2, result;

    /* check for proper number of arguments */
    if(nrhs != 2) {
        mexErrMsgIdAndTxt("MATLAB:sampleFunction:invalidNumInputs",
                          "Two inputs required.");
    }
    if(nlhs != 1) {
        mexErrMsgIdAndTxt("MATLAB:sampleFunction:invalidNumOutputs",
                          "One output required.");
    }

    /* ensure the inputs are scalar */
    if(!mxIsDouble(prhs[0]) || mxIsComplex(prhs[0]) ||
       !mxIsDouble(prhs[1]) || mxIsComplex(prhs[1]) ||
       mxGetNumberOfElements(prhs[0]) != 1 ||
       mxGetNumberOfElements(prhs[1]) != 1) {
        mexErrMsgIdAndTxt("MATLAB:sampleFunction:inputNotScalar",
                          "Both inputs must be scalar.");
    }

    /* get the value of the scalar inputs */
    num1 = mxGetScalar(prhs[0]);
    num2 = mxGetScalar(prhs[1]);

    /* perform the addition */
    result = num1 + num2;

    /* set the output pointer to the output matrix */
    plhs[0] = mxCreateDoubleScalar(result);
}

2. Compile the "mex" function using the following command:

mex sampleFunction.c

Once compiled, you can start calling “sampleFunction” in MATLAB.

I hope this helps, thanks!