User`s manual

Examples of C MEX-Files

2-9

if(!mxIsDouble(prhs[0]) || mxIsComplex(prhs[0]) ||

!(mrows == 1 && ncols == 1) ) {

mexErrMsgTxt("Input must be a noncomplex scalar double.");

}

/* Create matrix for the return argument. */

plhs[0] = mxCreateDoubleMatrix(mrows,ncols, mxREAL);

/* Assign pointers to each input and output. */

x = mxGetPr(prhs[0]);

y = mxGetPr(plhs[0]);

/* Call the timestwo subroutine. */

timestwo(y,x);

}

In C, function argument checking is done at compile time. In MATLAB, you can

pass any number or type of arguments to your M-function, which is responsible

for argument checking. This is also true for MEX-files. Your program must

safely handle any number of input or output arguments of any supported type.

To compile and link this example source file at the MATLAB prompt, type

mex timestwo.c

This carries out the necessary steps to create the MEX-file called timestwo

with an extension corresponding to the platform on which you’re running. You

can now call

timestwo as if it were an M-function.

x = 2;

y = timestwo(x)

y =

You can create and compile MEX-files in MATLAB or at your operating

system’s prompt. MATLAB uses

mex.m, an M-file version of the mex script, and

your operating system uses

mex.bat on Windows and mex.sh on UNIX. In

either case, typing

mex filename

at the prompt produces a compiled version of your MEX-file.