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TSFoster/tax

Created July 2, 2013 14:38
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Revisions

  1. TSFoster revised this gist Jul 2, 2013. No changes.
  2. TSFoster created this gist Jul 2, 2013.
    51 changes: 51 additions & 0 deletions tax
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,51 @@
    #!/usr/bin/env ruby
    # encoding: utf-8

    class TaxCalculator
    INFINITY = 1.0/0.0
    DEFAULT_RATES = {
    0.0...9440.0 => 0.0 ,
    9440.0...32010.0 => 0.2 ,
    32010.0...150000.0 => 0.4 ,
    150000.0..INFINITY => 0.45
    }

    def initialize rates=nil
    @rates = rates || DEFAULT_RATES
    end

    def earnings_from amount
    amount - tax_on(amount)
    end

    def tax_on amount
    @rates.inject(0.0) do |sum, (range, rate)|
    amount > range.first ? ([amount, range.last].min - range.first)*rate + sum : sum
    end
    end

    def to_earn amount
    @rates.sort{|(a,_),(b,_)|a.first<=>b.first}.reverse.each do |range, rate|
    e = earnings_from range.first
    return range.first + (amount-e)/(1-rate) if e < amount
    end
    end

    def to_be_taxed amount
    @rates.sort{|(a,_),(b,_)|a.first<=>b.first}.reverse.each do |range, rate|
    e = tax_on range.first
    return range.first + (amount-e)/rate if e < amount
    end
    end
    end

    tax_calculator = TaxCalculator.new

    command = ARGV[1] ? ARGV[0] : ARGV[0] ? 'tax_on' : nil
    amount = ARGV[1] ? ARGV[1] : ARGV[0] ? ARGV[0] : nil

    if ['earnings_from', 'tax_on', 'to_earn', 'to_be_taxed'].include? command
    puts "£%.2f" % tax_calculator.send(command, amount.to_f)
    else
    puts "USAGE tax [earnings_from|tax_on|to_earn|to_be_taxed] amount"
    end