From: Jim Weirich <jweirich@...>
Date: 2003-09-13T11:26:34+09:00
Subject: Re: OO Challenge

On Fri, 2003-09-12 at 10:57, Weirich, James wrote:

Not to beat a dead horse or anything, but I love playing with variations
on a theme...

I reviewed the thread that Henry posted.  Not much interesting except
that one fellow posted a Haskell version of the tax program.  Here it is
...

  tax_soldier earning = earning/10
  tax_professor earning = earning/15 + 100

  tax (TaxPayer earning taxgroups) =
      maximum (map (\f -> f earning) taxgroups)

  -? tax (TaxPayer 3000 [tax_soldier, tax_professor])

Wow, short and to the point.  So, could a Ruby version be that concise? 
Here's my attempt ...

  TaxSoldier = proc { |earning| earning / 10.0 }
  TaxProfessor = proc { |earning| earning / 15.0 + 100 }

  def tax(earning, tax_groups)
    tax_groups.collect { |g| g.call(earning) }.max
  end

  puts tax(3000, [TaxSoldier, TaxProfessor])

Pretty much a line for line translation.  Why so much shorter than
previous versions?  Because we threw out the tax payer abstraction and
just pass around earning (e.g. salary).

-- 
-- Jim Weirich       jweirich@one.net      http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)