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Re: The ". $" notation (was: 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.

Alan Manuel Gloria:
> To reduce the parentheses, we could (I propose!!) do:
> cut .
>   proc arg arg <> arg arg <...>

Ugh. I *really* don't see the value of this form, and
allowing "." at the end disables some error checking
I don't really want to disable.  Seems to me that
people would normally write:

cut proc arg arg <> arg arg <...>

I also suspect there may be implementation problems.

> Or alternatively:
> cut . $ proc arg arg <> arg arg <...>

I doubt I would *personally* use this, and I'm skeptical
that it adds much.  But on the other hand
I don't see any harm, especially since
we have to check after "." anyway for special cases, and
that seems like an improbable construct to use *accidentally*.

So I'd be okay with adding this.

Again, I'd just write:
cut proc arg arg <> arg arg <...>

> Basically, in the case of cut, while ". $" is effectively a no-op, it
> separates, syntactically, the procedure call from the form that
> provides a limited extension of the procedure call's semantics (in the
> case of cut, it adds <> and <...> syntaxes).  A user might, in the
> future, be able to think of other extended formulations which ". $"
> could then support.

> So my proposal is:
> 1.  Allow "foo . EOL INDENT x ..." ==> "(foo . (x ...))"

Worried about this one.

> 2.  Allow "foo . $ x ..." ==> "(foo x ...)"

I could get talked into this one, though I can't imagine using it.

> What does everyone think??

I'd sure like to know too!

--- David A. Wheeler