First separator for subassignments must be '.'

First separator for subassignments must be '.'

This pares down syntax supported since issue 4790 to match the allowed
usage from issue 4797.  Permitting ',' here seemed particularly
strange.

[thomasmorley651, 2018-10-03 16:56:27]

Even without your patch one can do:

part.1,1 = "foo"
part.1,2 = "bar"
part.1,3 = "buzz"
part.2,1 = "xx"
part.2,2 = "yy"
part.2,3 = "zz"
part.3   = "whatever"

#(format #t "\n\"part\" contains:\n~y\n" part)
#(format #t "Example call in guile: \"1\" of \"part\":\n~a" (assoc-get 1 part))
#(format #t "\nExample calls with ly-syntax:")

%% Working:
\void \displayScheme \part.2,3
\void \displayScheme \part.3

%% Causing errors:
% \void \displayScheme \part,1,1
% \void \displayScheme \part,1.1
% \void \displayScheme \part.1.1

I wasn't aware you can create nested lists with this syntax, already.

If I understand correctly your patch will disallow a first comma, forcing a dot
Will it force the comma as second separator?

[dak, 2018-10-03 17:19:45]

On 2018/10/03 16:56:27, thomasmorley651 wrote:
> Even without your patch one can do:
> 
> part.1,1 = "foo"
> part.1,2 = "bar"
> part.1,3 = "buzz"
> part.2,1 = "xx"
> part.2,2 = "yy"
> part.2,3 = "zz"
> part.3   = "whatever"
> 
> #(format #t "\n\"part\" contains:\n~y\n" part)
> #(format #t "Example call in guile: \"1\" of \"part\":\n~a" (assoc-get 1
part))
> #(format #t "\nExample calls with ly-syntax:")
> 
> %% Working:
> \void \displayScheme \part.2,3
> \void \displayScheme \part.3
> 
> %% Causing errors:
> % \void \displayScheme \part,1,1
> % \void \displayScheme \part,1.1
> % \void \displayScheme \part.1.1
> 
> I wasn't aware you can create nested lists with this syntax, already.
> 
> If I understand correctly your patch will disallow a first comma, forcing a
dot
> Will it force the comma as second separator?

No.  The errors you get for 1.1 are because 1.1 is a real number.  If you write
those 1 . 1 (not sure whether you can omit one or the other space) they will
work fine as well.  Enforcing stuff beyond the first dot/comma would make the
grammar more complex and I don't see that we'd accomplish anything by that. 
It's possible if it irritates people but would then also sacrifice \part.2,3 . 
I don't know whether that would ever be a problem, though.

[dak, 2018-10-03 17:27:43]

On 2018/10/03 16:56:27, thomasmorley651 wrote:
> Even without your patch one can do:

Oh, I forgot: "even without your patch" points to a misunderstanding.  The sole
purpose of this patch is to remove a previously accepted construct for
assignment because, well, I was troubled by a discussion pointing out that it
was accepted (though only in assignment, not in reference).

It doesn't seem either practically nor conceptually useful, there was no
discussion when I implemented it as part of another patch, and it seems like a
mistake to me now that I did so.