From: Daniel Waite <rabbitblue@...>
Date: 2008-05-08T04:51:22+09:00
Subject: Re: hash adding values

Tim Wolak wrote:
> Craig Demyanovich wrote:
>> I posted some code just before you replied. Did it help?
> 
> I did not store anything when I run it with my code I posted I get:
> 
> 
> {}
> {}
> {}

Hash.new { |hash, key| hash[key] = Array.new }

Is what you will need if you intend to provide arrays as default values 
to hashes.

So... (I've only skimmed your code, but I think I get the gist of your 
idea, so pardon if this isn't what you were asking for)

Basically, store the raw values, then you can sum and do any number of 
operations on them as you wish.

account_balances = Hash.new do |hash, key|
  hash[key] = Array.new
end

array_of_accounts.each do |account|
  accounts[account_name] << account.this_charge
  accounts[account_name] << account.that_charge
  ...
end

I'm going to say ab in place of account_balances here....

ab[some_account].sum # if using Rails, else try inject

ab[some_account.inject(BigDecimal.new) do |sum, amount|
  sum += amount
end
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