Refactor sym_step_i function

range.c

@@ -308,8 +308,8 @@ range_each_func(VALUE range, int (*func)(VALUE, VALUE), VALUE arg)
     }
 }
 
-static int
-sym_step_i(VALUE i, VALUE arg)
+static VALUE*
+step_i_iter(VALUE arg)
 {
     VALUE *iter = (VALUE *)arg;
 
@@ -319,6 +319,14 @@ sym_step_i(VALUE i, VALUE arg)
     else {
 	iter[0] = rb_funcall(iter[0], '-', 1, INT2FIX(1));
     }
+    return iter;
+}
+
+static int
+sym_step_i(VALUE i, VALUE arg)
+{
+    VALUE *iter = step_i_iter(arg);
+
     if (iter[0] == INT2FIX(0)) {
 	rb_yield(rb_str_intern(i));
 	iter[0] = iter[1];
@@ -329,14 +337,8 @@ sym_step_i(VALUE i, VALUE arg)
 static int
 step_i(VALUE i, VALUE arg)
 {
-    VALUE *iter = (VALUE *)arg;
+    VALUE *iter = step_i_iter(arg);
 
-    if (FIXNUM_P(iter[0])) {
-	iter[0] -= INT2FIX(1) & ~FIXNUM_FLAG;
-    }
-    else {
-	iter[0] = rb_funcall(iter[0], '-', 1, INT2FIX(1));
-    }
     if (iter[0] == INT2FIX(0)) {
 	rb_yield(i);
 	iter[0] = iter[1];