Re: initial .ly files [was Re: *.mid vs *.midi]

[Hans Aberg]

On 18 May 2008, at 00:24, Karl Hammar wrote:

> > This would walk down the path of C-like compilers.
>
> Is that a bad thing?

It means only that it might be a good idea to think very carefully  
before walking down that path :-). C is a very old language, with a  
simple setup, leaving much to the user how to pick things together.

> Actually what I would like is some way to tell on the command line  
> that
> this run should have /ancient fonts/c-clefs/modern clefs/... so I  
> could
> easily switch style without having to write a new file.

With a module system, one might write some like
  import font.ancient.c-clef.modern
which is easy enough to change from within the file.

Now, to fix this from the command line, one way is like in "make",  
setting variables which have effect within the program. In LilyPond,  
one might define a Scheme function with a constant, and define that  
constant from a startup argument, like in
  lilypond --scheme<...>
or something. Or it could be a a macro preprocessor like in C - M4 is  
a popular choice. But preprocessors are only there as a tool to fix  
things that cannot be hadnled from the language.

> > Have you checked out Haskell <http://haskell.org/> and the compiler
> > GHC? - Haskell has a module system, which makes it possible for GHC
> > to compile by
> >    ghc --make a.hs
> > where "a.hs" is a file containing a "main" function. By the module
> > system, it is possible to deduce what files to include. One then only
> > needs to set the library paths somewhere.
>
> There is some kind of "library path" in lilypond to find e.g.
> "gregorian-init.ly" which I don't have in the current directory.

The module import system is different from file includes in that the  
language knows what modules have been imported, and also keep names  
from different modules from clashing.

So, for example, one can make the order of module import declarations  
irrelevant. But with file include, one needs to make sure they are  
include in the right order.

  Hans