Moved select to detect to short on success

Arigeom/Guardfile

@@ -3,7 +3,7 @@
 
 guard 'rspec', :version => 2 do
   watch(%r{^spec/.+_spec\.rb$})
-  watch(%r{^lib/(.+)\.rb$})     { |m| "spec/lib/#{m[1]}_spec.rb" }
+  watch(%r{^lib/(.+)\.rb$})     { |m| "spec/#{m[1]}_spec.rb" }
   watch('spec/spec_helper.rb')  { "spec" }
 
   # Rails example

Arigeom/lib/arigeom.rb

@@ -1,15 +1,6 @@
 #!/usr/bin/env ruby
 
 class Arigeom
-  def permutations(set)
-    options = []
-    (2..set.length).each do |size|
-      o = set.combination(size).to_a
-      options += o
-    end
-    options
-  end
-
   def geometric_change(set)
     differ(set) do |cur, last|
       cur.to_f / last.to_f
@@ -23,30 +14,30 @@ def arithmetic_change(set)
   end
 
   def find_geometric(set)
-    combination_select(set) do |combi|
+    combination_detect(set) do |combi|
       geometric_change(combi)
-    end.last
+    end
   end
 
   def find_arithmetic(set)
-    combination_select(set) do |combi|
+    combination_detect(set) do |combi|
       arithmetic_change(combi)
-    end.last
+    end
   end
 
   private
 
-  def combination_select(set, &block)
+  def combination_detect(set, &block)
     selected  = []
-    (2..set.length).each do |size|
+    set.length.downto(2) do |size|
       set.combination(size).each do |s|
         changes = yield s
         if changes.uniq.size == 1
-          selected << s
+          return s
         end
       end
     end
-    selected
+    nil
   end
 
   def differ(set, &block)

Arigeom/spec/arigeom_spec.rb

@@ -2,24 +2,6 @@
 
 describe Arigeom do
   subject { described_class.new }
-  describe :permutations do
-    it "returns arrays of possibe sets for current length" do
-      result = subject.permutations [1,2,3,4]
-      result.to_a.should == [
-        [1,2],
-        [1,3],
-        [1,4],
-        [2,3],
-        [2,4],
-        [3,4],
-        [1,2,3],
-        [1,2,4],
-        [1,3,4],
-        [2,3,4],
-        [1,2,3,4]
-      ]
-    end
-  end
 
   describe :geometric_change do
     it "returns difference ratio between numbers" do