Merge pull request #2562 from cubicdaiya/issues/pow_flo

Fix and add test for Numeric#pow behavior.

src/numeric.c

@@ -54,11 +54,12 @@ static mrb_value
 num_pow(mrb_state *mrb, mrb_value x)
 {
   mrb_value y;
-  mrb_float d;
+  mrb_float d, yv;
 
   mrb_get_args(mrb, "o", &y);
-  d = pow(mrb_to_flo(mrb, x), mrb_to_flo(mrb, y));
-  if (mrb_fixnum_p(x) && mrb_fixnum_p(y) && FIXABLE(d))
+  yv = mrb_to_flo(mrb, y);
+  d = pow(mrb_to_flo(mrb, x), yv);
+  if (mrb_fixnum_p(x) && mrb_fixnum_p(y) && FIXABLE(d) && yv > 0)
     return mrb_fixnum_value((mrb_int)d);
   return mrb_float_value(mrb, d);
 }

test/t/numeric.rb

@@ -18,6 +18,14 @@ assert('Numeric#abs', '15.2.7.4.3') do
   assert_equal(1.0, -1.abs)
 end
 
+assert('Numeric#pow') do
+  assert_equal(8, 2 ** 3)
+  assert_equal(-8, -2 ** 3)
+  assert_equal(1, 2 ** 0)
+  assert_equal(1, 2.2 ** 0)
+  assert_equal(0.5, 2 ** -1)
+end
+
 assert('Numeric#/', '15.2.8.3.4') do
   n = Class.new(Numeric){ def /(x); 15.1;end }.new