[stringtemplate-interest] [antlr-interest] why "null" does not work (String Template)

[gaochunguang]

thank you.
----- Original Message ----- 
From: "Kay Röpke" <kroepke at classdump.org>
To: "gaochunguang" <gaochunguang at 163.com>
Cc: "ANTLR-Interest Interest" <antlr-interest at antlr.org>
Sent: Saturday, August 16, 2008 9:27 PM
Subject: Re: [antlr-interest] why "null" does not work (String Template)


Hi!
(setting reply-to to stringtemplate-interest because that's the  
appropriate place for this question).

On Aug 16, 2008, at 10:29 AM, gaochunguang wrote:

>
>  StringTemplate st = new
>       StringTemplate("<chars; wrap, null=\"0\">",
>       AngleBracketTemplateLexer.class);
>  st.setAttribute("chars", "a");
>  st.setAttribute("chars", "b");
>  st.setAttribute("chars", "c");
>  st.setAttribute("chars", null);
>  st.setAttribute("chars", "e");
>  st.setAttribute("chars", "f");
>  System.out.println(st.toString());
>
> output is abcef.


the setAttribute method ignores anything with a null value. I'm not  
sure what the rationale is behind that, but by writing it like:

        StringTemplate st = new
                 StringTemplate("<chars; wrap, null=\"0\">",
                 AngleBracketTemplateLexer.class);
         st.setAttribute("chars", new String[] {"a", "b", "c", null,  
"e", "f"});
         System.out.println(st.toString());

you get the output:
abc0ef

I believe ST should check if the attribute you want to set already is  
a multivalue container before discarding null values (but not null  
names obviously) in setAttribute(Object, Object), because in the  
current implementation it's not behaving consistently, as shown above.

cheers,
-k
-- 
Kay Röpke
http://classdump.org/