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Re: how useful are collecting lists?

This page is part of the web mail archives of SRFI 110 from before July 7th, 2015. The new archives for SRFI 110 contain all messages, not just those from before July 7th, 2015.

I said:
> > Hmm. If that's a *problem*, one solution without significantly changing
> > the existing semantics might be to allow <*...*> after ".".

Alan Manuel Gloria <almkglor@xxxxxxxxx> wrote:

> Ara ara, I thought this was *already* allowed...

Actually, they weren't.  I was trying to be picky about what's allowed after "." (e.g., I don't think "$" and "\\" are sensible), and obviously was *too* picky.  You're absolutely right, that should be permitted.

So this is an important tip, we need to allow this case. I've changed the BNF and Scheme implementation so that a collecting list is legal after the dot in "rest".  Thus, this is now legal:
define x . <*
! define y 5

! define z 6

I haven't modified "head", so if "." is the first atom on a line, a collecting list currently can't follow.  I can't figure out why you'd want to do that, I'd expect a user to just use a collecting list in that case.

So we already have an important comment (from David Vanderson) that's pointed out a problem, and I've posted a possible solution (one that I hope others will agree is sensible).  Excellent!  Seems to me that's why we have a SRFI process...

--- David A. Wheeler