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Re: How do feel people about the following change in syntax?

From: David Kastrup
Subject: Re: How do feel people about the following change in syntax?
Date: Wed, 12 Oct 2011 18:19:09 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux)

Graham Percival <address@hidden> writes:

> On Wed, Oct 12, 2011 at 05:42:47PM +0200, David Kastrup wrote:
>> I am currently trying to make music functions more powerful, in
>> particular their argument predicates.  Also I am trying to relieve the
>> parser from responsibilities.
> Looks basically good to me.  GLISS was never planned to tackle
> scheme stuff, and waiting for GLISS 2 would take 2 years or more
> at our current rate of progress.  I see no reason to postpone this
> change for that long.
>> Now I have a possibly slightly contentious change...  I want to let { }
>> mimic the new functionality of #{ #} instead of creating sequential
>> music unconditionally.  That means the following:
>>                       previously equivalent to    now equivalent to
>> { \with ... }         syntax error                context-modification
>> { c4 }                \sequential { c4 }          simple-music
> What happens if somebody writes
>   { \with foo    c4     \with bar    d4 }
> ?

Good catch.  I don't think we want anything but a syntax error here.
One approach would be not to ignore Scheme expressions in a sequence
unless they evaluate to "unspecified" or at least a limited set of
"ignorable" values.

More compatible would be the approach that you can omit braces only when
a certain construct is syntactically expected somewhere: if it is to be
produced "foreignly", use # or { ... }.  Then

{ { \with foo } c4 { \with bar } d4 }

would be a music sequence with two Scheme expressions inside getting
ignored, and { \with foo c4 \with bar d4 } would be a syntax error.

David Kastrup

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