Binding Variables¶

One of the bread-and-butter tasks in programming is handling variables. We already have seen predefined and custom variable definitions, but now it is time to have a closer look at the topic.

We have seen that symbols can be used as self-evaluating data or as references to something else: the quoted symbol 'red simply evaluates to that name while the symbol red evaluates to the list (1.0 0.0 0.0).

guile> 'red
red

guile> red
(1.0 0.0 0.0)

The usual Scheme terminology for the latter case is to say that “the name red evaluates to that list” and that “the list is bound to the variable/name red”.

In the case of red this binding is available because it has been created explicitly somewhere in the LilyPond initialization files, but when we need our own variable name, say violet evaluating to (0.5 0.0 1.0), we have to “create the binding” ourselves.

Bindings can be created at top-level or locally, which we'll investigate in the following chapters.