User`s manual

2 Creating C Language MEX-Files

2-6

For example, if you invoke a MEX-file from the MATLAB workspace with the

command

x = fun(y,z);

the MATLAB interpreter calls mexFunction with the arguments

plhs is a 1-element C array where the single element is a null pointer. prhs is

a 2-element C array where the first element is a pointer to an

mxArray named

Y and the second element is a pointer to an mxArray named Z.

The parameter

plhs points at nothing because the output x is not created until

the subroutine executes. It is the responsibility of the gateway routine to create

an output array and to set a pointer to that array in

plhs[0]. If plhs[0] is left

unassigned, MATLAB prints a warning message stating that no output has

been assigned.

Note It is possible to return an output value even if nlhs = 0. This

corresponds to returning the result in the ans variable.

nlhs = 1

nrhs = 2

plhs

prhs

•