Determine whether array represents data as signed 64-bit integers
Logical 1 (true) if the array stores its data as signed 64-bit integers, and logical 0 (false) otherwise.
Use mxIsInt64 to determine whether the specified array represents its real and imaginary data as 64-bit signed integers.
In C, calling mxIsInt64 is equivalent to calling:
mxGetClassID(pm) == mxINT64_CLASS
In Fortran, calling mxIsInt64 is equivalent to calling:
mxGetClassName(pm) == 'int64'