Hilbert curve: Difference between revisions

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 (make-curve 500 6 7 30 (make-color 255 255 0) (make-color 0 0 0))</lang>
+=={{header|Ruby}}==
+{{libheader|RubyGems}}
+{{libheader|JRubyArt}}
+<br/>
+Implemented as a Lindenmayer System, depends on JRuby or JRubyComplete
+<lang Ruby>
+attr_reader :hilbert
+def settings
+  size 600, 600
+end
+def setup
+  sketch_title '2D Hilbert'
+  @hilbert = Hilbert.new
+  hilbert.create_grammar 5
+  no_loop
+end
+def draw
+  background 0
+  hilbert.render
+end
+class Grammar
+  attr_reader :axiom, :rules
+  def initialize(axiom, rules)
+    @axiom = axiom
+    @rules = rules
+  end
+  def apply_rules(prod)
+    prod.gsub(/./) { |token| rules.fetch(token, token) }
+  end
+  def generate(gen)
+    return axiom if gen.zero?
+    prod = axiom
+    gen.times do
+      prod = apply_rules(prod)
+    end
+    prod
+  end
+end
+class Hilbert
+  include Processing::Proxy
+  attr_accessor :grammar, :axiom, :draw_length, :production, :turtle
+  DELTA = Math::PI / 2
+  XPOS = 0 # placeholders for turtle
+  YPOS = 1
+  THETA = 2
+  def initialize
+    @axiom = 'FL'
+    @grammar = Grammar.new(
+      axiom,
+      'L' => '+RF-LFL-FR+',
+      'R' => '-LF+RFR+FL-'
+    )
+    @draw_length = 200
+    stroke 0, 255, 0
+    stroke_weight 2
+    @turtle = Array.new(3) # using an array as turtle
+    turtle[XPOS] = width / 9
+    turtle[YPOS] = height / 9
+    turtle[THETA] = 0
+  end
+  def render
+    production.scan(/./) do |element|
+      case element
+      when 'F' # NB NOT using affine transforms
+        draw_line(turtle)
+      when '+'
+        @turtle[THETA] += DELTA
+      when '-'
+        @turtle[THETA] -= DELTA
+      when 'L'
+      when 'R'
+      else puts 'Grammar not recognized'
+      end
+    end
+  end
+  def draw_line(turtle)
+    x_temp = turtle[XPOS]
+    y_temp = turtle[YPOS]
+    @turtle[XPOS] += draw_length * Math.cos(turtle[THETA])
+    @turtle[YPOS] += draw_length * Math.sin(turtle[THETA])
+    line(x_temp, y_temp, turtle[XPOS], turtle[YPOS])
+  end
+  def create_grammar(gen)
+    @draw_length *= 0.6**gen
+    @production = @grammar.generate gen
+  end
+end
+</lang>
 =={{header|Scala}}==