Recommendations on avoiding range pipeline type hell

[Chris Piker]

On Saturday, 15 May 2021 at 14:05:34 UTC, Paul Backus wrote:

> If you post your code (or at least a self-contained subset of 
> it) someone can probably help you figure out where you're 
> running into trouble. The error messages by themselves do not 
> provide enough information--all I can say from them is, "you 
> must be doing something wrong."

I just tacked on `.array` in the the unittest and moved on for 
now, but for those who may be interested in the "equivalent but 
not equivalent" dmd error message mentioned above, the code is up 
on github.  To trigger the error message:

```bash
git clone git at github.com:das-developers/das2D.git
cd das2D
rdmd -unittest --main das2/range.d  # This works
```
In file `das2/range.d`, comment out lines 550 & 553 and uncomment 
lines 557 & 558 to get alternate definitions of `coarse_recs` and 
`fine_recs` then run rdmd again:

```bash
rdmd -unittest --main das2/range.d  # No longer works
```

In addition to the issue mentioned above, comments on any style 
issues, best practices or design choices are invited.  By the way 
the writeln calls in the unittests just temporary.