int (*create_window_function)(sqlite3*,const char*,int,int,void*,
void (*xStep)(sqlite3_context*,int,sqlite3_value**),
void (*xFinal)(sqlite3_context*),
void (*xValue)(sqlite3_context*),
void (*xInv)(sqlite3_context*,int,sqlite3_value**),
void(*xDestroy)(void*));
int (*create_window_function)(sqlite3*,const char*,int,int,void*,
void (*xStep)(sqlite3_context*,int,sqlite3_value**),
void (*xFinal)(sqlite3_context*),
void (*xValue)(sqlite3_context*),
void (*xInv)(sqlite3_context*,int,sqlite3_value**),
void(*xDestroy)(void*));