TITLE: Syntax for const


PROBLEM: iis@netcom.com (International Imaging Syste)

I would like to code a function which has a pointer argument; I would like to
express the fact that the function will not change the value of the pointer.
 
I tried the expression
     int f (const T* arg_name);
The compiler would not let me do anything meaningful with arg_name, it seemed
to be trying to protect *arg_name from change.  What I'm trying to do is
protect arg_name itself from change.

I tried the expression
     int f (const (T*) arg_name);
But this is a syntax error.

Your suggestions?


RESPONSE: grumpy@cbnewse.cb.att.com (Paul J Lucas), AT&T Bell Laboratories
	  11 May 93

read C++ from right-to-left

   T const *p;                     // p is a pointer to a const T
   T *const p;                     // p is a const pointer to T
   T const *const p;               // p is a const pointer to a const T
                                                            
Since the pointer is a local, having a const pointer is useless.
Also, you can reverse the order of T and const:     

   const T *p === T const *p;
                                                            
I prefer the latter.