From: Gavin Sinclair <gsinclair@...>
Date: 2012-01-13T14:11:55+09:00
Subject: Re: Turning a case/when into a Hash (for a yaml file)

On Fri, Jan 13, 2012 at 2:50 PM, Marc Heiler <shevegen@linuxmail.org> wrote:
> x = 4_924
>
> case x
> when 0..100
>  1
> when 101..500
>  2
> when 501..1_000
>  3
> when 1_001..5_000
>  4
> when 5_000..1_000_000
>  5
> else
>  0
> end
>
> I would like to turn the above into:
>
> (a) a hash instead
> (b) store it into a yaml file.

Each of the "when" conditions is a range object.  The "else" condition
is obviously not.  Range objects can be a key in a hash, so you can
have (untested)

  { 0..100 => 1, 101..500 => 2, ..., :else => 0 }

and that Hash can be stored as YAML.

Then you need to write a method

  def level_for_xp(hash, xp)
    ...
  end

which is easily done.

Rather than a hash, I would go for an array of arrays:

  [ [0..100, 1], [101..500, 2], ..., [:else, 0] ]

Reason: preserve order.  I know the current implementation of Ruby's
hashes does preserve insertion order, but that's an implementation
detail.  For this usage, preserving order is a conceptual detail.

Gavin