Wishlist: some way to control output serialization

[Klortho]

This is another to-do item from the vault.

Here's an example from a post by John Clyman on comp.languages.perl.modules (http://tinyurl.com/7hy6p4u):

  use Number::Scale;
  my $basic_si = Number::Scale->SI;
  print $basic_si->scale(1024); '1 K'
  my $si_bytes = $basic_si->new(
     unit => ['byte', 'B'],
     trunc => 2,
  );
  print $si_bytes->(1024); # '1 KB'
  my $si_distance = $basic_si->new(
     unit => ['meter', 'M'],
     trunc => 2,
  );
  my $si_weight = $basic_si->new(
     unit => ['gram', 'G'],
     trunc => 2,
  );
  my $std_distance = Number::Scale->StandardDistance;
  print $std_distance->scale(25); # '2 feet 1 inch'
  my $std_weight = Number::Scale->StandardWeight;
  print $std_weight->scale(18); # '1 pound 2 ounces'

[Klortho]

This would involve some way to encode systems of units. Something like this, maybe:

InitSystem (
    'si', [ qw(m kg s newton square-meter cubic-meter watt joule
               pascal m/s coulomb volt farad ohm siemens tesla weber henry)
          ],
    'cgs', [ qw(cm gm s dyne square-centimeter cubic-centimeter watt
                erg dynes-per-square-centimeter centimeters-per-second)
           ],
    'english', [ qw(foot slug s pound square-foot cubic-foot horsepower
                    foot-pound pounds-per-square-inch feet-per-second)
               ],
);

[jberger]

A few things to note, your first system is not SI, but rather MKS. SI uses grams not kilograms. I think that if this was a goal, it would fit in with having loadable databases per instance. One would make a Physics::Unit object, load a units database and set the units system. I think this is a worthy goal, but a major undertaking.

[Klortho]

your first system is not SI, but rather MKS

According to Wikipedia, it is kilograms.

Another system that we'll definitely want support for is the Furlong/Firkin/Fortnight (FFF) system. :)

[jberger]

Well I stand corrected, NIST

[Klortho]

There are other very good ways to specify output serialization.

Here's how Math::Units::PhysicalValue does it:

print ($rate + "0 miles/hour"), "\n" # prints 103.07 miles/hour

Another would be a method to produce an output using the best SI prefix. Quoting jpierce on RT: "Since you already have prefix to exponent mapping, it would be mighty handy to have a method of taking a result like 1.055056e+18 (joules) and getting back: 1.055056, exa(joules)."