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Re: [xml-dev] InnerXml is like printf (WAS: Underwhelmed)

From: Miles Sabin <miles@----------.--->
To: Arjun Ray <aray@----.--->, xml-dev@-----.---.---
Date: 9/22/2002 10:52:00 AM
Arjun Ray wrote,
> | InnerXml _is_ printf ... but that doesn't mean we couldn't have
> | something analogous to printf which has its nice features (domain-
> | specific little language) without the risk of non-well-formedness.
>
> I suppose by "nice features" you mean variable substitution, which is
> the value of a template.  I also assume that there's protection
> against the classic printf disaster of short arglists.

Err ... no, not especially. I mean that the template syntax can fit the 
job, rather than having to be shoe-horned into the host languages 
syntax (example later).

> I think the bigger fight is not with Java syntax, but with GP
> expectation. The default mindset first time in the door is probably
> one of "I gotta write strings, why can't I write strings?"

Hire smarter programmers?

>   1.  &Deity; forbid that I should make a mistake in *xpath* syntax!
>       (who catches that, how, and when?  Looks like runtime to me.)

Sure, at runtime ... tho' presumably the _first_ runtime, so it's not 
too dreadful.

>   2.  How do I splice other stuff?  Or do I have to put the entire
>       tree into a single expression?

How about,

  Element link =
    new Element(
     "link[@rel='stylesheet',@type='text/css',@href=%0]",
     { "/ss/style.css" } );

  Element e =
    new Element(
      "html/("+
        "head/(title/text(%0),%1),"+
        "body/text(%2))",
      { "Example 3", link, "Hello World" } );

>   3.  What about adding more than one child to an element?

Already in that example (head and body, title and link). Like I said, 
this is a mish-mash of XPath and s-exprs.

>   4.  Do concise arrays allow a mixture of heterogenous objects? How
>       do substitute subtrees in?

Yup, and illustrated above.

> I'm really not convinced this is a win.  Not to mention that XPath
> reeks too much of Obligatory HighTech.  I have to write a xpath-expr
> parser too just to support this?  Aiyaiyai!

Probably _you_ don't. An implementor of such an API could do it just the 
once, and it'd be applicable across all vocabularies. OTOH you'd have 
to write (or generate) a new library for every vocabulary. FWIW, I 
don't think code generation is going to do a very good job without 
manual intervention, cp. JAXB's mapping schemas.

> | Oh, and BTW: Hungarian notation is an abomination ;-)
>
> I agree (it wasn't quite Hungarian notation, except perhaps for the
> 'e' prefix on the locals).  Hungarian notation is a decent idea taken
> to a ridiculous extreme.
>
> The 'a' prefix on element construction methods and 'w' (for "with")
> on attribute methods were necessary in order to prevent clashes with
> Java reserved words.

This is the example of fighting the host languages syntax I alluded to 
earlier. There are a few nasty examples in the HTML DOM.

Cheers,


Miles

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