Using the C Math Library

Restoring the Previous Context 

Each function that you write must close with a call to mlfRestorePreviousContext(). Place the call just before the return statement for your function.

The call operates on the output and input array arguments passed to your function. It ensures that the memory allocated for those arrays is restored to its state at the time of the function call.

Note    You can't return from your function before calling mlfRestorePreviousContext(), and you can call mlfRestorePreviousContext() only once in your function.

Prototype:

void mlfRestorePreviousContext(int nout, int nin, ...);

Sample Call from Template:

mlfRestorePreviousContext(1,2,output_arg1, input_arg1, input_arg2);

Arguments to mlfRestorePreviousContext( )

mlfRestorePreviousContext() takes the number of output arguments, the number of input arguments, and a variable-length list of the actual output and input arguments to the function. You do not need to terminate the list of arguments with a NULL argument.

Pass the same arguments to mlfRestorePreviousContext() as you passed to mlfEnterNewContext():

1. The number (int nout) of array output arguments declared by your function. Specify 0 if there are no array output arguments declared (in the same way the main() template function does).

The template function declares one output argument.

2. The number (int nin) of array input arguments declared by your function. Specify 0 if there are no array output arguments declared (in the same way the main() template function does).

The template function declares two input arguments.

3. The array output arguments (mxArray **) themselves, in the order declared for the function.

In the template, output_arg1 is passed.

4. The array input arguments (mxArray *) themselves, in the order declared for the function.

In the template, input_arg1 and input_arg2 are passed.

Note    You only list mxArray** and mxArray* arguments. For example, if a function takes an argument of type char* or int, do not include it in the count of output and input arguments or in the list of the arguments themselves.

What Happens to the Array Arguments?

mlfRestorePreviousContext() restores the state of the input arrays to their state at the time of the function call:

• Any array input argument that was temporary at the time of the function call becomes temporary again.
• Any array input argument that was bound at the time of the function call remains bound.

mlfRestorePreviousContext() then performs an important action: it deletes any input array arguments that are temporary.

Note    mlfRestorePreviousContext() recognizes when the current function is called from a function that does not use automated memory management. In that call context, where all arrays are temporary, it does not delete any arrays.

Purpose of mlfRestorePreviousContext( )

This is the key step that allows a call to another function to be embedded as an input argument to your function. Your function deletes the temporary arrays passed to it, ensuring proper deletion of the memory for temporary arrays.

Deleting Bound Arrays

Returning an Array