Bugfix: risky macro definition caused counter problems.

Bugfix: risky macro definition caused counter problems.

Macros should be used sparingly, if at all.
When macros are used, they should be used carefully.

In this case, I was defining a variable "i".
The substituted data also included an "i", which caused a non-obvious problem.

Use a more unique counter variable name "_macro__i" to help avoid these problems in the future.