[stringtemplate-interest] Strange tail-recursive behaviour

[VAUCHER Laurent]

  Hi,

  I'm currently trying StringTemplate (v2.2 downloaded yesterday oct 11)
and trying a kind of tail-recursive template, I stumbled upon the
following behaviour.

  I have a template group file that reads :
--- "mytest/main.stg" ----------------------
group main;

/* Root template  */
root(place) ::= <<

<namestail(place)>

>>

/* Tail template  */
namestail(x) ::= <<

<if(x)>
++++
TRUE:<x>
TRUE:<x>
first(PLACE)=<first(x)>
rest(PLACE)=<rest(x)>
TAIL CALL:
<namestail(x=rest(x))>
<else>
-----
FALSE:<x>
<endif>

>>
---------------------------------------------



  and a simple driver class




----- "Main.java" ---------------------------
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.text.SimpleDateFormat;
import java.util.Date;

import org.antlr.stringtemplate.StringTemplate;
import org.antlr.stringtemplate.StringTemplateGroup;
import org.antlr.stringtemplate.language.AngleBracketTemplateLexer;

public class Main {

  /**
   * @param args
   */
  public static void main(String[] args) {
    System.out.println(new SimpleDateFormat().format(new Date()));

    try {
      FileReader reader = new FileReader("src/mytest/main.stg");
      StringTemplateGroup stg = new StringTemplateGroup(reader,
          AngleBracketTemplateLexer.class);
  
      StringTemplate firstST = stg.getInstanceOf("root");
      firstST.setAttribute("place", "A");
      firstST.setAttribute("place", "B");
  
      System.out.println("Generated [" + firstST.toString() + "]");
    } catch (FileNotFoundException eFNFE) {
      eFNFE.printStackTrace(System.err);
    }
  }
}
--------------------------------------------


   And the output is :


------------- output -----------------------
12/10/05 15:37
Generated [

++++
TRUE:AB
TRUE:AB
first(PLACE)=A
rest(PLACE)=B
TAIL CALL:

++++
TRUE:B
TRUE:
first(PLACE)=
rest(PLACE)=
TAIL CALL:

-----
FALSE:
]
--------------------------------------------

  What I find annoying is the inner call to namestail : the value of x
changes from a line to the next. The first "TRUE:<x>" yields "TRUE:b",
the second "TRUE:" as if the value had been swallowed by the first <x>.
As you can see, the outer invocation of namestail does not seem
afflicted...

  Is there something I am missing (dynamic scoping can be tricky, I
know) ?



Laurent.