InnerXml is like printf (WAS: Underwhelmed)

[Miles Sabin <miles@milessabin.com>]

Elliotte Rusty Harold wrote,
> At 10:40 AM -0600 9/21/02, Aaron Skonnard wrote:
> > Yes, both MSXML and the .NET implementation have supported this
> > through the Inner/OuterXml properties.
>
> Now that you mention it, I have seen that. I had filed it away at the
> back of my brain as "horrid, ugly, non-standard extensions to
> JavaScript and DOM" and promptly forgotten it once I finished working
> at the company that was using it.

That's always been my reaction too.

But on reflection (and playing devils advocate a bit) maybe it's not as 
unreasonable as it seems. It has quite a lot in common with printf- 
style IO APIs, which despite being error-prone (and occasionally the 
source of security vulnerabilities) have proved to be surprisingly 
resistant to replacement by more structured, typesafe or object- 
oriented APIs.

To illustrate, compare,

  const char* s = "printf";
  int i = 2;
  puts(s);
  puts(" is ");
  putint(i); // pretend this is standard C
  puts(" times more usable\n");

  vs.

  const char* s = "printf";
  int i = 2;
  printf("%s is %i times more usable\n", s, i);

with,

  String s = "InnerXml";
  int i = 2;
  Element usability = new Element("usability");
  usability.add(new Attribute("factor", Integer.toString(i)));
  usability.appendChild(s);

  vs.

  String s = "InnerXml";
  int i = 2;
  parent.appendChild("<usability factor=\"+2+"\">"+s+"</usability>");

Why do these string-template approaches support such dramatically more 
compact and readable code? I think it's simply because the syntax of 
the template-strings provides a domain-specific "little language" which 
is better tuned to the task at hand than the generic mechanisms 
provided by the host language. I guess things like embedded SQL, for 
all their ugliness, do much the same job.

So maybe the answer would be to come up with a template string syntax 
that's more idiomatic for XML than printf style. How about something 
XPath-like? For example,

  String s = "XPath expansion";
  int i = 2;
  parent.appendChild("usability[@factor="+i+"]/text("+s+")");

or if we waited for J2SE 1.5 which'll have auto-boxing and concise array 
literals, we could even have,

  parent.appendChild("usability[@factor=%i]/text(%s)", {i, s});

Thoughts?

Cheers,


Miles