Using C library, function with fucntion pointer as a parameter.
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I want to make use of a C library in MATLAB but one of the main functions that the library requires has as a parameter a pointer function.
The library that I am using is proprietary so I can not share too much info, I'll try to explain it with a simpler library.
The reason I need the function pointer is because the library does not know how to find the square root of a number, so I need to make a function in MATLAB for finding the square root of a number, then pass a pointer to that function to the library using a function. Since other functions in the library need to know how to do the square root of a number it needs this function to be able to use the rest of the library.
Sorry about the wierd example. I hope this is clear enough. And I just wanted to know if this was possible.
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James Tursa
2026-7-13，18:09
编辑：James Tursa
2026-7-18，18:23
I'm assuming your real function is not actually sqrt(), else you would just call a C math library function for this. But my example will use sqrt() per your request.
You will probably need to write a C-function wrapper for your MATLAB function, then pass a pointer to that function. E.g., something like this:
/* mex_example.c
* Bare bones MATLAB function wrapper example.
* Would need extra argument and return checking for production code.
*/
#include "mex.h"
/* This would be the signature from the header for your library */
/* Takes a function pointer as input and returns a double */
double library_function( double (*mfunction)(double) );
/* This is the C-wrapper function that your library function will call */
double myfunction(double x)
{
double y;
mxArray *rhs[1];
mxArray *lhs[1];
rhs[0] = mxCreateDoubleScalar(x);
if( mexCallMATLAB( 1, lhs, 1, rhs, "matlab_sqrt") ) /* callback to MATLAB */
{
mexErrMsgTxt("The MATLAB function callback failed!");
}
y = mxGetScalar(lhs[0]);
mxDestroyArray(rhs[0]);
mxDestroyArray(lhs[0]);
return y;
}
/* The MATLAB gateway function */
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
double y;
y = library_function( myfunction );
plhs[0] = mxCreateDoubleScalar( y );
}
/* This is the function in your library that takes a function pointer */
double library_function( double (*mfunction)(double) )
{
double x = 2.0; /* Example data created here for simplicity */
double y = mfunction( x );
return y;
}
The MATLAB matlab_sqrt.m file used for the callback is simply this:
function y = matlab_sqrt(x)
y = sqrt(x);
end
Compiling and running this:
>> mex mex_example.c
Building with 'MinGW64 Compiler (C)'.
MEX completed successfully.
>> mex_example
ans =
1.4142
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