Criado Free Context Grammar e Chomsky Normal Form

lib/chomsky_normal_form.rb

@@ -0,0 +1,17 @@
+require 'free_context_grammar'
+
+class ChomskyNormalForm < FreeContextGrammar
+
+  def initialize(v, t, p, s)
+    super(v, t, p, s)
+  end
+
+  def valid?
+    @productions.values.each do |p|
+      p.each do |vp|
+        vp.scan
+      end
+    end
+  end
+end
+

lib/free_context_grammar.rb

@@ -0,0 +1,21 @@
+require 'chomsky_normal_form'
+
+class FreeContextGrammar
+  attr_accessor :vars, :terms, :productions, :start
+
+  def initialize(v, t, p, s)
+    @vars = v # ['E']
+    @terms = t # ['+', '*', '[', ']', 'x']
+    @productions = p # { 'E' => ["E+E", "E*E", "[E]", "x"] }
+    @start = s # 'E'
+  end
+
+  def start_productions
+    @productions[@start]
+  end
+
+  def to_cnf
+
+  end
+end
+

test/unit/chomsky_normal_form_test.rb

@@ -0,0 +1,56 @@
+require 'test/unit'
+require 'rubygems'
+require 'shoulda'
+require File.dirname(__FILE__) + '/../../lib/free_context_grammar'
+require File.dirname(__FILE__) + '/../../lib/chomsky_normal_form'
+
+class ChomskyNormalFormTest < Test::Unit::TestCase
+
+  context 'Invalid CNF' do
+    should 'be invalid' do
+      cnf = ChomskyNormalForm.new(
+        ['E'],
+        ['+', '*', '[', ']', 'x'],
+        { 'E' => ["E+E", "E*E", "[E]", "x"] },
+        'E'
+      )
+      assert !cnf.valid?
+    end
+  end
+
+  context 'Valid CNF' do
+    should 'be valid' do
+      cnf = ChomskyNormalForm.new(
+        ['A', 'B'],
+        ['a', 'b', 'c'],
+        { 'A' => ['AB', 'B'], 'B' => ['a'] },
+        'A'
+      )
+      assert cnf.valid?
+    end
+  end
+=begin
+  should "resolv example 10 from the book" do
+    fcg = FreeContextGrammar.new(
+      ['E'],
+      ['+', '*', '[', ']', 'x'],
+      { 'E' => ["E+E", "E*E", "[E]", "x"] },
+      'E'
+    )
+    fnc_converted = fcg.to_fnc
+
+    fnc_expected = ChomskyNormalForm.new(
+      ['E', 'C+', 'C*', 'C[', 'C]', 'D1', 'D2', 'D3']
+      ['+', '*', '[', ']', 'x'],
+      {
+        'E' => ['ED1', 'ED2', 'C[D3', 'x'],
+        'D1' => ['C+E'], 'D2' => ['C*E'], 'D3' => ['EC]'],
+        'C+' => ['+'], 'C*' => ['*'], 'C[' => ['['], 'C]' => [']']
+      },
+      'E'
+    )
+    
+    assert_equal fnc_expected, fnc_converted
+  end
+=end
+end

test/unit/free_context_grammar_test.rb

@@ -0,0 +1,26 @@
+require 'test/unit'
+require 'rubygems'
+require 'shoulda'
+require File.dirname(__FILE__) + '/../../lib/free_context_grammar'
+
+class FreeContextGrammarTest < Test::Unit::TestCase
+  context "The first free context grammar example" do
+    setup do
+      @fcg = FreeContextGrammar.new(
+        ['E'],
+        ['+', '*', '[', ']', 'x'],
+        { 'E' => ["E+E", "E*E", "[E]", "x"] },
+        'E'
+      )
+    end
+
+    should "accept free context grammar object" do
+      assert @fcg
+    end
+
+    should "get the start production" do
+      assert_equal @fcg.start_productions, ["E+E", "E*E", "[E]", "x"]
+    end
+  end
+end
+