Re: What is the problem with "\relative"? (Was: Do we really offer the future?)

[Thomas Morley]

2015-04-23 3:41 GMT+02:00 Kieren MacMillan <address@hidden>:
> Hi Gilles,
>
>>> deprecate \relative, which I now avoid like the plague.
>> Why?
>
> 1. It doesn’t play well with reuse: both trivial reuse (i.e., cut-and-paste) 
> and more advanced (i.e., referenced in variables) require extra care at the 
> very least, and outright extra work (e.g., octave checks, transposition, 
> etc.) in most cases. This means that sharing bits of music either within a 
> file/piece or between files/pieces (or even between users) requires extra 
> work and is error-prone.
>
>
> 2. It makes what should be simple adjustments unnecessarily complicated, with 
> unnecessarily large impacts. Consider, as just one example, my paired 
> functions
>
> split =
> #(define-music-function (parser location music1 music2)
>    (ly:music? ly:music?)
>    #{ <<
>          { \voiceOne $music1 }
>          \context Voice = "2" { \voiceTwo $music2 }
>       >> \oneVoice
>    #})
>
> splitLU =
> #(define-music-function (parser location music1 music2)
>    (ly:music? ly:music?)
>    #{ <<
>          { \voiceTwo $music1 }
>          \context Voice = "2" { \voiceOne $music2 }
>       >> \oneVoice
>    #})
>
> These (and their 3- and 4-voice counterparts) are workhorses in my code, 
> saving me endless amounts of typing constructs like
>
>     << { \voiceOne foo } \new Voice { \voiceTwo bar } >> \oneVoice
>
> every time I simply want a short polyphonic section. I could hardly begin to 
> do efficient engraving work without them. Now consider the effect of 
> switching, in relative mode, from
>
>    b4 \split { a4 } { c,4 }
>
> to
>
>    b4 \splitLU { c,4 } { a4 }
>
> Because relative mode “leaves from” whatever pitch comes immediately before 
> it, the first example would output the b followed by a sixth “chord" 
> immediately below it (i.e., with the a on top, sitting a second below the b), 
> whereas the second example would output the b followed by a third [!!] 
> “chord" (i.e., with the c, on top, sitting a seventh below the b). In 
> absolute mode, I am free to choose either function (and each is necessary!) 
> at will, without worrying that the choice may mess up the outputted pitches.
>
> This same sort of relative shifting happens when you want to switch the order 
> of notes as given in a chord, e.g. <c g’ b> outputs a different chord than <c 
> b g’>.
>
>
> 3. Many single edits suddenly require two (or more) edits as a result solely 
> of relative mode. For example, let’s say you have
>
>     \relative c’ { c d e a }
>
> and you want to change the e to d. Now you must also add an apostrophe to the 
> a, to compensate for the relative octave adjustment:
>
>     \relative c’ { c d d a’ }
>
> wasting effort and brainpower (if you even remember to do it the first time, 
> rather than compiling before finding the error).
>
>
> These are only three of the problems. Worst of all, having it is a false 
> economy: it’s not actually intuitive for everyone (though it is for me, and 
> was right away), as a quick search of the archives will turn up many newbies 
> complaining about “how hard it is to remember when to use , and when to use ‘ 
> and when to use nothing”.
>
> Yes, it’s a little more work during initial entry of some music to add the 
> correct octavation to the pitches. But the majority of pitches I enter fall 
> between c, and b’’, so the difference (if any) is minimal. And of course 
> there are many patterns which require *more* octavation typing in relative 
> mode than absolute, so in those cases absolute mode saves keystrokes.
>
> Hope this helps explain why I don’t use \relative any more, and tell most 
> newbies I know to avoid it.
>
> Cheers,
> Kieren.
>
> ________________________________
>
> Kieren MacMillan, composer
> ‣ website: www.kierenmacmillan.info
> ‣ email: address@hidden
>



Hi all,

I'm a little late to the party...

One very annoying thing about \relative is when you want to use
music-functions catching some music doing something with it.

Here the less complex function I could think of, returning different
results for absolute and relative.
(It's only a show-case, the functionality could be achieved easily
with other predefined commands, but I hope you'll get the point.)

repeat-note =
#(define-music-function (parser location music)(ly:music?)
  (make-sequential-music (list music (ly:music-deep-copy music))))

\absolute { c'1 \repeat-note c'' }
\relative c' { c \repeat-note c'1 }

Btw, it _can_ be made to work properly with both input modes, needs
some additional coding, though.

Cheers,
  Harm