I'm writing a reporting module, which allows a (knowledgeable) user to specify the content and format of a report in HTML/Excel/XML/PDF etc, without having to touch the code.

For instance, this report would return a list of order_line objects - one for each row, then proceed to write out each column in the row, based on the current order_line object:

I would have a %vars hash which would contain (eg) the $lang variable and and would store the row variables $order_line, $order and $product, and a %function hash, which would contain the lookup() and currency() code refs.


    title:          This week's order lines
    object_type:    order_line
    query:
                    ... query params that return a list of Object IDs 
+...
    row_vars:
        order:      $order_line.order                   # Stores $orde
+r 
        product:    $order_line.product                 # and $product
+ in the %vars hash
    columns:
        -
            title:  Order
            value:  $order.id                           # $order->id
        -
            title:  Order date
            value:  $order.create_date.yMonthd($lang)   # $order->crea
+te_date->yMonthd($lang)
        -
            title:  Order total
            value:  $order.total | currency             # currency ($o
+rder->total)
            format:
                    align:  right
        -
            title:  Invoice no
            value:  $order.invoice_id || 'Not invoiced' 
        -
            title:  Pickup address
            value:  $order_line.pickup_id 
                        ? $order_line.pickup_id | lookup ('pickup',$la
+ng,$order_line.pickup_id)
                        : $order_line.pickup_text

[download]

The question: how should I parse the value fields?

The value fields are short, discreet strings, in a TT style. The grammar is limited, but allows for quite a lot of flexibility.

My first inclination was to use a few regexes and to string together some coderefs, the return value from the previous coderef being passed as an argument to the next coderef. This would be fine, until I hit the logical operators (&& || ?:). Suddenly, this introduced the concept of branching into the code.

It feels like it should be a small job, and so I have been loathe to load up a full parser to do it. Having read Higher Order Perl, I have considered using Dominus' HOP::Parser, but I'm wondering if I should bite the bullet and use one of the standard modules like Parse::RecDescent or Parse::Yapp.

I have no experience with any of these modules. What would you recommend to handle what (in my ignorant opinion) should be a light-weight parsing task?

thanks

Clint

UPDATE : I have now posted my parser here: A parser for a limited grammar

In reply to How to parse a limited grammar by clinton

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