使用mex进行混合编程的一些注意事项
1、mxGetPr的使用：

Use mxGetPr on arrays of type double only. Use mxIsDouble to validate the mxArray type. For other mxArray types, use mxGetData.

In C, mxGetData returns a void pointer (void *). Since void pointers point to a value that has no type, you must cast the return value to the pointer type that matches the type specified by pm. To see how MATLAB? types map to their equivalent C types, see the table on the mxClassID reference page.