From: Lennon Day-Reynolds <rcoder@...>
Date: 2004-08-14T05:58:05+09:00
Subject: Re: Question: A method for summing several variables

Harry,

In that case, most of the nicer ways to do what you're looking for in
Ruby are going to unavailable -- the whole reason that container types
like arrays and hashes are in the core language is to make tasks like
this easier.

The best recommandation I'd have for you would be to define the sets
of fields you're going to be working with as arrays, which will still
give you some advantages. You'll have to manually list the fields you
want to work with, but you can quickly perform operations on those
entire lists, at least.

For example, instead of writing 'box1_X = (box1_2 + box1_4 + ...)', do
something like the following:

current_boxset = [box1_2, box1_4, <...>]
sum_of_boxset = current_boxset.inject(0.0) {|sum, current| sum += current.to_f}
box1_X = sum_of_boxset

(etc.)

This will be especially useful if you define the sets of fields you're
working with in some central place, and can maintain those datasets
seperately from the algorithmic code that operates on them; it would
even free you up to use more structured types later, so long as the
algorithms eventually got the array of strings they expected.

I'm not sure how often you need operations like 'sum' that operate
over a list of values, but you can also add a convenience method to
the Array type to clean up the uses of the code:

class Array
  def sum(initial=0.0)
    self.inject(initial) {|sum, current| sum += current}
  end
end

...and use it like this:

my_array = [ '1.2', '3', '4.5' ]
sum = my_array.map { |val| val.to_f}.sum


Lennon
rcoder.net

P.S.: If you don't mind me asking, why the hard requirement that you
stick with the unstructured variable types? Just stuck with the legacy
code, or is there some sinister force at work?