On 3/11/07, Christoffer Lern=F6= <lerno@dragonascendant.com= > wrote:

Fun Quiz!<= br>
Here's my solution (ASCII only I'm afraid). I use a wrapper = object to
handle a neighbourhood. Since I only allow access one at a time, I
s= imply recycled a single object. This is unsafe in the general case,
but = works nicely here I think.

My code for rotations are explicit than c= alculated, but I find it
easier to read and understand what is going on.

#!/usr/bin/e= nv ruby -w

module SimFrost

   class FrostGrid
     attr_reader :data

    = ; def initialize(width, height, percent)
     &= nbsp; @width, @height =3D width, height
       @data =3D Array.new(height) { Arra= y.new(width) { rand * 100 <
percent ? '.' : ' ' }.joi= n }
       self[width / 2, height / 2] =3D= ?*
       @neighbourhood =3D Neighbourhoo= d.new(self)
       @tick =3D 0
     end

     def [](x, = y)
       @data[y % @height][x % @width]     end

     def []=3D(x,= y, value)
       @data[y % @height][x % @= width] =3D value
     end

   &= nbsp; def tick
       @tick +=3D 1
       vapour =3D 0
   =     each_neighbourhood do |neighbourhood|
  &nb= sp;      neighbourhood.mutate
   = ;      vapour +=3D 1 if neighbourhood.contains_vap= our?
       end
    = ;   vapour
     end

  &nb= sp; def draw_freeze
       draw # Before we start freezing       draw while tick > 0
  = ;     draw # After everything is frozen
  =    end

     def draw
  &n= bsp;    puts "Tick: #{@tick}"
   = ;    puts "+" + "-" * @width + "+&q= uot;
       @data.each { |row| puts "|#{r= ow}|" }
       puts "+" + &= quot;-" * @width + "+"
     end
     def each_neighbourhood
   &nbs= p;   @tick.step(@tick + @height, 2) do |y|
         @tick.step(@tick + @wi= dth, 2) do |x|
         &nb= sp; yield @neighbourhood[x, y]
       = ; end
       end
  &nbs= p; end

   end

   class Neighbourhoo= d

     2.times do |y|
    = ;   2.times do |x|
         class_eval &quo= t;def xy#{x}#{y}; @grid[@x + #{x}, @y + #{y}]; end"
  &nb= sp;      class_eval "def xy#{x}#{y}=3D(v); @g= rid[@x + #{x}, @y + #{y}]
=3D v; end"
    &n= bsp; end
     end

   &nb= sp; def initialize(grid)
       @grid =3D grid
  &nbs= p; end

     def [](x, y)
  &n= bsp;    @x, @y =3D x, y
     &nb= sp; self
     end

     de= f ccw90
       self.xy00, self.xy10, self.= xy01, self.xy11 =3D xy10, xy11, xy00,
xy01
     e= nd

     def cw90
     = self.xy00, self.xy10, self.xy01, self.xy11 =3D xy01, xy00, xy11,
= xy10
     end

     def ea= ch_cell
       @y.upto(@y + 1) { |y| @x.up= to(@x + 1) { |x| yield x, y } }
     end

     def contains?(c)
   &nbs= p;   each_cell { |x, y| return true if @grid[x, y] =3D=3D c }
=        false
     end<= br>
     def contains_ice?
   &nbs= p;   contains? ?*
     end

&n= bsp;   def contains_vapour?
       contains? ?.
   &nbs= p; end

     def freeze
   &nbs= p;   each_cell { |x, y| @grid[x, y] =3D ?* if @grid[x, y] =3D=3D = ?. }
     end

     def ro= tate_random
       rand < 0.5 ? ccw90 := cw90
     end

     def mutate
      = contains_ice? ? freeze : rotate_random
     end
=
     def to_s
     &nbs= p; "+--+\n+" << xy00 << xy10 << "+\n+"= ; << xy01 << xy11 << "+\n+--+"
     end
   end

  = ; def SimFrost.simfrost(width, height, percent =3D 50)
   = ; FrostGrid.new(width, height, percent).draw_freeze
   e= nd

end

if __FILE__ =3D=3D $PROGRAM_NAME
   SimFr= ost::simfrost(40, 20, 35)
end