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D - extension for printf

reply Ben Hinkle <bhinkle4 juno.com> writes:
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
Mar 09 2004
next sibling parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
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
  

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/
Mar 09 2004
parent "Ben Hinkle" <bhinkle4 juno.com> writes:
 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
Mar 09 2004
prev sibling parent "Ben Hinkle" <bhinkle4 juno.com> writes:
 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).
Mar 09 2004