> I don’t see why one is better than the other. 

I was surprised that the ellipsis which 'x' varies over changes between the 
pattern and the template. But it looks like no one else has the same 
intuition, so it's fine :-).

> Yes. See this part of the documentation of `syntax`: 

That's clear, thanks. I should have looked that up before asking.

On Wednesday, March 28, 2018 at 7:59:42 AM UTC-4, Matthew Flatt wrote:
> Just to answer some parts of the original question: 
> At Tue, 27 Mar 2018 13:01:54 -0700 (PDT), Justin Pombrio wrote: 
> > I'm surprised by the behavior of using a pattern variable under one set 
> of 
> > ellipses in the pattern, and under two sets of ellipses in the template: 
> > [...] 
> > Is this the expected behavior? 
> Yes. See this part of the documentation of `syntax`: 
>  If a pattern variable is replicated by more <ellipsis>es in a template 
>  than the depth marker of its binding, then the pattern variable’s 
>  result is determined normally for inner <ellipsis>es (up to the 
>  binding’s depth marker), and then the result is replicated as 
>  necessary to satisfy outer <ellipsis>es. 
> > And is there a good reason for it? 
> If I remember correctly, I implemented a different behavior first, but 
> switched to be consistent with the `syntax-case` implementation. I also 
> vaguely remember that the switch made things work better. That was a 
> long time ago, though, so I may not remember correctly. 

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