Re: Shortcut for \repeat unfold

[Jean Abou Samra]

Le 29/09/2021 à 01:50, Dan Eble a écrit :
> > On Sep 24, 2021, at 19:32, Jean Abou Samra <jean@abou-samra.fr> wrote:
> >
> > Other possibilities:
> >
> > - "\rep n music", not as self-telling (and I think Lukas
> >    only calls his shortcut \rep because redefining \repeat
> >    is not syntactically valid);
> > - "music * n", attractive but the difference between c1*5
> >    and { c1 } * 5 would be confusing; also, for longer passages
> >    one would rather state the number of repetitions from the
> >    start than having to remember to put it at the end;
> > - "\* n music", very short but doesn't read as nicely I think,
> >    and I don't view repeats as special enough to warrant
> >    this kind of syntax with many special characters.
> > Thoughts?
> 28x { d a b fs | g d g a }
>
> https://gitlab.com/lilypond/lilypond/-/merge_requests/937

That is a clever proposal. I am already fond of it.
Thank you.


> I like that, thanks!  Carl's concerns w.r.t. whitespace are valid,
> though.  Would it be possible to make the invalid syntax '28 x'
> produce a nice error message like
>
>    invalid <whatever>,  did you mean '28x'?


It's not unconceivable to build whitespace into the
lexer pattern and have { 5 x c'1 } work.

diff --git a/lily/lexer.ll b/lily/lexer.ll
index a1556480d3..f13211cde1 100644
--- a/lily/lexer.ll
+++ b/lily/lexer.ll
@@ -178,7 +178,7 @@ COMMAND             \\{SYMBOL}
 SPECIAL                [-+*/=<>{}!?_^'',.:]
 SHORTHAND      (.|\\.)
 UNSIGNED       {N}+
-REPEAT_COUNT    {UNSIGNED}x
+REPEAT_COUNT    {UNSIGNED}{WHITE}*x
 E_UNSIGNED     \\{N}+
 FRACTION       {N}+\/{N}+
 INT            -?{UNSIGNED}
@@ -582,7 +582,7 @@ FIG_ALT_EXPR 
{WHITE}*{FIG_ALT_SYMB}({FIG_ALT_SYMB}|{WHITE})*
                return UNSIGNED;
        }
        {REPEAT_COUNT}  {
-               yylval = scm_c_read_string (YYText ());
+               yylval = scan_repeat_count (YYText ());
                return REPEAT_COUNT;
        }
        \\\"    {
@@ -642,7 +642,7 @@ FIG_ALT_EXPR 
{WHITE}*{FIG_ALT_SYMB}({FIG_ALT_SYMB}|{WHITE})*
                return UNSIGNED;
        }
        {REPEAT_COUNT}  {
-               yylval = scm_c_read_string (YYText ());
+               yylval = scan_repeat_count (YYText ());
                return REPEAT_COUNT;
        }
        -  {
@@ -818,7 +818,7 @@ FIG_ALT_EXPR 
{WHITE}*{FIG_ALT_SYMB}({FIG_ALT_SYMB}|{WHITE})*
 }

 {REPEAT_COUNT} {
-       yylval = scm_c_read_string (YYText ());
+       yylval = scan_repeat_count (YYText ());
        return REPEAT_COUNT;
 }

@@ -1398,7 +1398,8 @@ scan_fraction (string frac)
 SCM
 scan_repeat_count (string s)
 {
-       s.pop_back (); // remove the 'x'
+       while (!isdigit (s.back ()))
+               s.pop_back (); // remove the 'x' and whitespace
        return scm_c_read_string (s.c_str ());
 }


What this means is that if you create a custom note
name language (with the undocumented not-yet-having-interface
#(set! language-pitch-names (acons 'mylang my-pitch-alist
language-pitch-names))), you won't be able to call a
note 'x', because

{ c4 x4 }

will be understood as

{ c 4x 4 }

I don't see that as a big deal. Using 'r' or 'R' or 'q'
as a note name is already not supported. To me, the
addition of this shorthand is worth a new element on
this list.

Thanks,
Jean