Question

Given an arbitrarily nested data structure, how can I create a new data structure so that all the elements in it have been standardized by applying a function on all the elements depending on the type of the element. For example, I might have

$data = {
    name => 'some one',
    date => '2010-10-10 12:23:45',
    sale => [34, 22, 65],
    cust => {
        name => 'Jimmy',
        addr => '1 Foobar Way',
        amnt => 452.024,
        item => ['books', 'pens', 'post-it notes']
    }
}

and I want to convert all text values to upper case, all dates to UTC date times, find the square of all integers, round down all real numbers and add 1, and so on. So, in effect, I want to apply a different function to each element depending on the type of element.

In reality the data might arrive via a database query, in which case they are already a Perl data structure, or they might start life as a JSON object, in which case I can use JSON::from_json to convert it to a Perl data structure. The idea is to standardize all the values in the data structure based on the value type, and then spit out the Perl data structure back again as a JSON object.

I read the answers to executing a function on every element of a data structure and feel that Data::Rmap might do the trick, but can’t figure out how. Seems like Rmap works on all the keys as well, not just the values.

Answer 1

It’s crazy straightforward with Data::Rmap you mentioned.

use Data::Rmap qw( rmap );
rmap { $_ = transform($_); } $data;

---

Regarding the question in the comments:

use Data::Rmap   qw( rmap );
use Scalar::Util qw( looks_like_number );

# Transforms $_ in place.
sub transform {
   if (looks_like_number($_)) {
      if (...) {
         $_ *= 2;
      }

      $_ = 0+$_;  # Makes it look like a number to JSON::XS
   } else {
      ...
   }
}

&rmap(\&transform, $data);