1.1.1 Scheme sandbox

The LilyPond installation includes the Guile implementation of Scheme. A hands-on Scheme sandbox with all of LilyPond loaded is available with this call on the command line:

lilypond scheme-sandbox

Once the sandbox is running, you get the Guile prompt

lily-guile@()>

to enter Scheme expressions. In the following, however, we use the shorter string guile> to indicate the prompt.

The file containing the sandbox code (ly/scheme-sandbox.ly) tries to activate the GNU readline library for nicer editing on the prompt (for example, using the up- and down-arrow keys to access previously typed commands). Currently, this only works with a LilyPond binary dynamically linked with Guile, which is not the case for the ‘officially’ distributed binaries. Two possible workarounds are as follows.

• Use rlwrap, a thin wrapper around the readline library. This program is available for Unix-like operating systems; call it with

  rlwrap lilypond scheme-sandbox
  

• Use the Emacs editor in combination with the LilyPond Tree-sitter Mode. This works under Windows, too.