Re: Accessing values from a multiple subrule repeition

On Wednesday, Feb 4, 2004 PerlDiscuss - Perl Newsgroups and mailing lists 
said:
> 
> With the following code fragment, I realise I can access the array
> containing the term values using the notation $item[2] as shown below:
> 
> SimpleExpression : term (AddOperator )(s?)
> {
> 	my $SimpleExpressionArray = $item[2];
> 	my @SimpleExpression =  @$SimpleExpressionArray;
> }
> 
> However, if I have repetition of multiple statements  such as (AddOperator
> term )(s?) as show below. How can I access both the AddOperator values,
> and the term values. If I access $item[2] as in the above example, it only
> contains the term rule values and the AddOperator values apear to be lost.
> 
> SimpleExpression : term (AddOperator term )(s?)
> {
> }
> 
> I apologise if I have not included enough detail, I have tried to be
> direct and to the point. Please let me know if you require more detail.
> 
> Paul Kennerley
> 

Based on your code fragment the answer is "you can'".  Or at least not 
without knowing what AddOperator and term are returning.

If you want a higher parsing expression to know what a lower parsing 
expression is *doing*, the lower parsing expression has to tell it.

This can be done either with global variables (a *bad* idea) or with return 
values.

What does AddOperator and term return in their respective code fragments?  If 
they *both* return something interesting it should be in the $item[n] array.  
Remember that what $item contains depends on what you coded, so you get the 
data structure you coded.

Try returning what you want, and also try using Data::Dumper to make it clear 
what was returned.

For example, in the code above, do this:

SimpleExpression : term (AddOperator )(s?)
{
	my $SimpleExpressionArray = $item[2];
	my @SimpleExpression =  @$SimpleExpressionArray;
        $DB::single=1; # breakpoint
        1;
}

and invoke perl with the debugger (i.e. -d switch).  When you hit the 
"breakpoint", you can use Data::Dumper to print out the entire recursive 
contents of @item and it will show you what is there.

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