5.2.3 Types of properties
So far we have seen two types of property: ‘number’ and
‘symbol’. To be valid, the value given to a property
must be of the correct type and obey the rules for that type.
The type of property is always shown in parentheses after the
property name in the IR. Here is a list of the types you may
need, together with the rules for that type, and some examples.
You must always add a hash symbol, #
to the front of these values when they are entered in the
\override command, even if the value itself already
starts with #. We only give examples for constants
here: if you want to compute a value using Scheme, see
Calculations in Scheme.
| Property type | Rules | Examples |
|---|
| Boolean | either ‘true’ or ‘false’, represented by #t or
#f | #t, #f |
dimension
(in staff spaces) | a decimal number (in units of staff spaces) | 2.5, 0.34 |
| direction | a valid direction constant or its numerical equivalent
(value 0 or CENTER indicate a neutral
direction) | LEFT, CENTER, UP, 1, -1 |
| integer | a whole number | 3, -1 |
| list | a sequence of constants or symbols separated by spaces, enclosed
in parentheses and preceded by an apostrophe (quote mark) | '(left-edge staff-bar),
'(1), '(),
'(1.0 0.25 0.5) |
| markup | any valid markup | \markup { \italic "cresc." }, "bagpipe" |
| moment | a musical length; this type is distinct from a note
duration | \musicLength 4.,
\musicLength { 2 2. } |
| number | any positive or negative, possibly decimal, value | 3, -2.45 |
pair
(of numbers) | two numbers separated by the sequence ‘whitespace’,
‘.’, ‘whitespace’, enclosed in parentheses, and
preceded by an apostrophe | '(2 . 3.5),
'(0.1 . -3.2) |
| symbol | any of the set of permitted symbols for that property,
preceded by an apostrophe | 'italic, 'inside |
| unknown | a procedure, or #f to cause no action | bend::print,
ly:text-interface::print,
#f |
| vector | constants enclosed in #(…). | #(#t #t #f) |
See also
Extending: Scheme tutorial.