Extract ruby_version comparison

Author: pitr-ch

ext/concurrent/extconf.rb

@@ -11,7 +11,7 @@ def create_dummy_makefile
   end
 end
 
-if defined?(JRUBY_VERSION) || ! Concurrent.allow_c_extensions? 
+if Concurrent.on_jruby? || ! Concurrent.allow_c_extensions?
   create_dummy_makefile
   warn 'C optimizations are not supported on this version of Ruby.'
 else

lib/concurrent/synchronization/object.rb

@@ -3,13 +3,14 @@ module Synchronization
     Implementation = case
                      when Concurrent.on_jruby?
                        JavaObject
-                     when Concurrent.on_cruby? && (RUBY_VERSION.split('.').map(&:to_i) <=> [1, 9, 3]) <= 0
+                     when Concurrent.on_cruby? && Concurrent.ruby_version(:<=, 1, 9, 3)
                        MonitorObject
-                     when Concurrent.on_cruby?
+                     when Concurrent.on_cruby? && Concurrent.ruby_version(:>, 1, 9, 3)
                        MutexObject
                      when Concurrent.on_rbx?
                        RbxObject
                      else
+                       warn 'Possibly unsupported Ruby implementation'
                        MutexObject
                      end
     private_constant :Implementation

lib/concurrent/utility/engine.rb

@@ -16,6 +16,16 @@ def on_rbx?
     def ruby_engine
       defined?(RUBY_ENGINE) ? RUBY_ENGINE : 'ruby'
     end
+
+    def ruby_version(comparison, major, minor, patch)
+      result      = (RUBY_VERSION.split('.').map(&:to_i) <=> [major, minor, patch])
+      comparisons = { :== => [0],
+                      :>= => [1, 0],
+                      :<= => [-1, 0],
+                      :>  => [1],
+                      :<  => [-1] }
+      comparisons.fetch(comparison).include? result
+    end
   end
 
   extend EngineDetector