2.3.1 Context evaluation
Contexts can be modified during interpretation with Scheme code. The syntax for this is
\applyContext function
function should be a Scheme function that takes a
single argument: the context in which the \applyContext
command is being called. The following code will print the
current bar number on the standard output during the compile:
\applyContext
#(lambda (x)
(format #t "\nWe were called in barnumber ~a.\n"
(ly:context-property x 'currentBarNumber)))