Merge pull request #2655 from tmtm/fix-numeric-step

Fix: Numeric#step infinite loop.

mrblib/numeric.rb

@@ -101,13 +101,21 @@ module Integral
   # incremented by +step+ (default 1).
   #
   def step(num, step=1, &block)
+    raise ArgumentError, "step can't be 0" if step == 0
     return to_enum(:step, num, step) unless block_given?
 
     i = if num.kind_of? Float then self.to_f else self end
+    if step > 0
       while(i <= num)
         block.call(i)
         i += step
       end
+    else
+      while(i >= num)
+        block.call(i)
+        i += step
+      end
+    end
     self
   end
 end