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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