Drop dependency from `mruby-rational` to `mruby-numeric-ext`

mrbgems/mruby-rational/mrbgem.rake

@@ -4,5 +4,4 @@ MRuby::Gem::Specification.new('mruby-rational') do |spec|
   spec.summary = 'Rational class'
 
   spec.add_dependency 'mruby-object-ext', core: 'mruby-object-ext'
-  spec.add_dependency 'mruby-numeric-ext', core: 'mruby-numeric-ext'
 end

mrbgems/mruby-rational/mrblib/rational.rb

@@ -83,7 +83,7 @@ end
 def Rational(numerator = 0, denominator = 1)
   a = numerator
   b = denominator
-  a, b = b, a % b until b.zero?
+  a, b = b, a % b until b == 0
   Rational._new(numerator.div(a), denominator.div(a))
 end
 

mrbgems/mruby-rational/test/rational.rb

@@ -100,3 +100,10 @@ assert 'Float#==(Rational), Float#!=(Rational)' do
   assert_equal_rational(true, -2.0, Rational(4,-2))
   assert_equal_rational(false, 3.3, Rational(13,4))
 end
+
+assert 'Rational#negative?' do
+  assert_predicate(Rational(-2,3), :negative?)
+  assert_predicate(Rational(2,-3), :negative?)
+  assert_not_predicate(Rational(2,3), :negative?)
+  assert_not_predicate(Rational(0), :negative?)
+end