currency.rb

# Proof of concept
e = 2
c = 10**e

amt = 5.67
amt_i = (amt * c).to_i
amt_f = amt_i.to_f / c

tax = 11
tax_f = tax.to_f / 100

amt_tax = amt_f * tax_f

puts "sub-total: #{sprintf("$%.#{e}f", amt_f)}"
puts "tax: #{sprintf("$%.#{e}f", amt_tax)}"
puts "total: #{sprintf("$%.#{e}f", amt_f + amt_tax)}"
puts '--'

# Class implemtation
class Currency
   def initialize(exp = 2, symbol = '$')
      @exp = exp
      @cent = 10**@exp
      @symbol = symbol
   end
   
   def amount_to_i(float)
      return (float * @cent).to_i
   end
   def amount_to_f(int)
      return int.to_f / @cent
   end
   def amount_to_s(int)
      "#{sprintf("#{@symbol}%.#{@exp}f", (int.to_f / @cent))}"
   end
end

usd = Currency.new(2, '$')
puts i = usd.amount_to_i(2.4)
puts f = usd.amount_to_f(i)
puts s = usd.amount_to_s(i)
puts '--'

itl = Currency.new(3, '₤')
puts i = itl.amount_to_i(2.4)
puts f = itl.amount_to_f(i)
puts s = itl.amount_to_s(i)
puts '--'

jpy = Currency.new(0, '¥')
puts i = jpy.amount_to_i(2400)
puts f = jpy.amount_to_f(i)
puts s = jpy.amount_to_s(i)
puts '--'