Re: try except in lilypond

[Andrew Bernard]

Hi Mike and Joram,

On 19 November 2016 at 21:06, Mike Solomon <address@hidden> wrote:

One thing I've used in the past for this sort of thing are Scheme functions, specifically file-exists? .

https://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/File-Manipulation.html

Another solution is to use some sort of top-level compilation script in bash or python, which is how i manage style sheets for large scores (I generate temporary ly files on the fly).

​

Since lilypond uses Guile 1.8 and not MIT Scheme, you may be better off looking here for file system functions:

https://www.gnu.org/software/guile/docs/docs-1.8/guile-ref/File-System.html#File-System

[Although I myself often derive useful inspiration from looking at other Scheme implementations.]

Joram,

Exceptions are not built in to Scheme but you can implement them in a library yourself with continuations if you are keen.

For example:

http://courses.cs.washington.edu/courses/cse341/04wi/lectures/15-scheme-continuations.html

This is not particularly trivial stuff, but it works. In general though functional programmers tend to avoid exception style coding, for a long list of reasons. But that's another story and probably another separate mailing list (lilypond-scheme anybody :-)).

As to actually implementing exceptions around lilypond code, I have not tried it so I cannot fully answer your question.

Andrew