Main Content

mexFunction (Fortran)

Entry point to Fortran MEX function

Fortran Syntax

#include "fintrf.h"
subroutine mexFunction(nlhs, plhs, nrhs, prhs)
integer nlhs, nrhs
mwPointer plhs(*), prhs(*)



Number of expected output mxArrays


Array of pointers to the expected output mxArrays


Number of input mxArrays


Array of pointers to the input mxArrays. Do not modify any prhs values in your MEX file. Changing the data in these read-only mxArrays can produce undesired side effects.


mexFunction is not a routine you call. Rather, mexFunction is the name of the gateway subroutine in Fortran which every MEX function requires. For more information, see Components of Fortran MEX File. When you invoke a MEX function, MATLAB® finds and loads the corresponding MEX function of the same name. MATLAB then searches for a symbol named mexFunction within the MEX function. If it finds one, it calls the MEX function using the address of the mexFunction symbol. MATLAB displays an error message if it cannot find a routine named mexFunction inside the MEX function.

When you invoke a MEX function, MATLAB automatically seeds nlhs, plhs, nrhs, and prhs with the calling arguments. In the syntax of the MATLAB language, functions have the general form:

[a,b,c,...] = fun(d,e,f,...)

where the ... denotes more items of the same format. The a,b,c... are left-side output arguments, and the d,e,f... are right-side input arguments. The arguments nlhs and nrhs contain the number of left side and right side arguments, respectively. prhs is an array of mxArray pointers whose length is nrhs. plhs is an array whose length is nlhs, where your function must set pointers for the output mxArrays.


It is possible to return an output value even if nlhs = 0, which corresponds to returning the result in the ans variable.


See these examples in matlabroot/extern/examples/mex:

Version History

Introduced before R2006a