Here's another proposal for an extensible stream.printf:

add the conversion specifier %D (for D object). This
specifier will call the object's print method. If
object.d also got a print method that accepted
options then %D could support formats like %20D etc.

Right now stream.printf just calls the underlying
printf with the entire format string. To support
%D stream.printf would have to go through the format
string and call the underlying printf for standard
conversions and dispatch any time it sees %D. Similar
code would work for printf-like functions like sprintf.

If this works out I'd like to change print in object.d
to just something like printf("[Object %p]",this);
instead of the current printf("Object %p\n",this);

I don't recall seeing this proposed before but I
could be wrong.

thoughts?

-Ben

Ben Hinkle wrote:

>Here's another proposal for an extensible stream.printf:
>
>add the conversion specifier %D (for D object). This
>specifier will call the object's print method. If
>object.d also got a print method that accepted options then %D could support formats like %20D etc.
>
>Right now stream.printf just calls the underlying printf with the entire format string. To support
>%D stream.printf would have to go through the format
>string and call the underlying printf for standard
>conversions and dispatch any time it sees %D. Similar
>code would work for printf-like functions like sprintf.
>
>If this works out I'd like to change print in object.d
>to just something like printf("[Object %p]",this); instead of the current printf("Object %p\n",this);
>
>I don't recall seeing this proposed before but I
>could be wrong. 
>
>thoughts?
>
>-Ben
>  
>
Good idea!

And if a D string is being used it would be able to format that properly without using %.*s.  It could also do an array of objects (since in D there is a distinction between arrays and pointers).

-- 
-Anderson: http://badmama.com.au/~anderson/

> And if a D string is being used it would be able to format that properly without using %.*s.  It could also do an array of objects (since in D there is a distinction between arrays and pointers).

Strings and arrays wouldn't be able to use the %D specifier since they
aren't objects and don't have a "print" method. Using %s for D strings
is possible but then it wouldn't work for C strings. So in that case
to print a C string you call std.c.printf("%s",...) and to print a D string
you call stdout.printf("%s",...). That doesn't look too bad to me, though
I haven't thought about the details. Printing arrays of arbitrary types is
probably best left to the user.

-Ben

> If this works out I'd like to change print in object.d
> to just something like printf("[Object %p]",this);
> instead of the current printf("Object %p\n",this);

oops - I meant print(..) not printf(...). And maybe the brackets
[Object %p] isn't that great since it might look like an array.
I haven't thought too much about object.print vs object.printf...

Walter, why did you choose object.print? I assume it's because printf takes a format string (hence the "f" in printf).