• BCS <ao pathlink.com> May 17 2007
• Chris Nicholson-Sauls <ibisbasenji gmail.com> May 17 2007
• BCS <ao pathlink.com> May 17 2007

BCS <ao pathlink.com> writes:

I have a struct like this

Struct
{
void go(T)(T v){}
}

and I want to only allow access to go with a finite set of parameters. My 
first thought was this:

Struct
{
private void goT(T)(T v){}
public alias goT!(int) go;
public alias goT!(char) go;
public alias goT!(byte) go;
public alias goT!(float) go;
}

But you cant tunnel through private with a public alias. Does anyone known 
of a clean get somthing like this? Wrapper functions are not an option.

Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:

BCS wrote:
 I have a struct like this
 
 Struct
 {
 void go(T)(T v){}
 }
 
 and I want to only allow access to go with a finite set of parameters. 
 My first thought was this:
 
 Struct
 {
 private void goT(T)(T v){}
 public alias goT!(int) go;
 public alias goT!(char) go;
 public alias goT!(byte) go;
 public alias goT!(float) go;
 }
 
 But you cant tunnel through private with a public alias. Does anyone 
 known of a clean get somthing like this? Wrapper functions are not an 
 option.
 
 


I don't know of any way to expose public names for private things in quite that
way, but 
you might consider something like this:

private void goT(T)(T v){
   static if (!(is(T == int) || is(T == char) || is(T == byte) || is(T ==
float))) {
     static assert (false, "...useful message...");
   }

   // ... code ...
}

Not super pretty, I know, but it should work.  It would be nice if there were a
cleaner 
way of doing this for those cases where the list is long.  (I have something I
would've 
liked to templatize in a similar fashion, but with about 10 types to support.)

-- Chris Nicholson-Sauls

BCS <ao pathlink.com> writes:

Reply to Chris Nicholson-Sauls,

 I don't know of any way to expose public names for private things in
 quite that way, but you might consider something like this:
 
 private void goT(T)(T v){
 static if (!(is(T == int) || is(T == char) || is(T == byte) || is(T
 == float))) {
 static assert (false, "...useful message...");
 }
 // ... code ...
 }
 Not super pretty, I know, but it should work.  It would be nice if
 there were a cleaner way of doing this for those cases where the list
 is long.  (I have something I would've liked to templatize in a
 similar fashion, but with about 10 types to support.)
 


Yeah, I guess I could do that. But I also have a bunch of other stuff that 
 would have to be checked. I guess I could make it all public and then make 
threats against the lives on anyone who uses the template directly. :b