Re: [Lilypond-auto] Issue 2607 in lilypond: Patch: Allow immediate Scheme expressions to take multiple values

[David Kastrup]

"Trevor Daniels" <address@hidden> writes:

>> Comment #16 on issue 2607 by address@hidden: Patch: Allow immediate Scheme  
>> expressions to take multiple values
>> http://code.google.com/p/lilypond/issues/detail?id=2607
>> 
>> Good idea documenting this, though.  That way people have a chance to  
>> notice.
>
> :)  I've noticed, and I've read it, twice, but I still don't understand
> it sufficiently to formulate a sensible comment.  Sorry :(

Then the documentation is insufficient.

$@(list a b ...) is equivalent to $a $b $...

The inspiration for this ,@ is described as

     If an `(unquote-splicing <expression> ...)' form appears inside a
     <qq template>, then the <expression>s must evaluate to lists; the
     opening and closing parentheses of the lists are then "stripped
     away" and the elements of the lists are inserted in place of the
     `UNQUOTE-SPLICING' form.

     Any `UNQUOTE-SPLICING' or multi-operand `UNQUOTE' form must appear
     only within a list or vector <qq template>.

     The following abbreviations may be used:

          (quasiquote <qq template>)       =  `<qq template>
          (unquote <expression>)           =  ,<expression>
          (unquote-splicing <expression>)  =  ,@<expression>

     Examples:

          `(list ,(+ 1 2) 4)                      => (list 3 4)

          (let ((name 'a))
            `(list ,name ',name))                 => (list a (quote a))

          `(a ,(+ 1 2) ,@(map abs '(4 -5 6)) b)   => (a 3 4 5 6 b)

          `((foo ,(- 10 3))
            ,@(cdr '(c)) . ,(car '(cons)))        => ((foo 7) . cons)

          `#(10 5 ,(sqrt 4) ,@(map sqrt '(16 9)) 8)
                                                  => #(10 5 2 4 3 8)

Suggestions for improving the docs?

-- 
David Kastrup