### A.12.5 Conditionals

`\if` condition? (procedure) argument (markup)

Test condition, and only insert argument if it is true. The condition is provided as a procedure taking an output definition and a property alist chain. The procedure is applied, and its result determines whether to print the markup. This command is most useful inside `oddHeaderMarkup` or similar. Here is an example printing page numbers in bold:

```\paper {
\markup \fill-line {
""
\if #print-page-number
\bold \fromproperty #'page:page-number-string
}
\markup \fill-line {
\if #print-page-number
\bold \fromproperty #'page:page-number-string
""
}
}
```
`\unless` condition? (procedure) argument (markup)

Similar to `\if`, printing the argument if the condition is false.

The following example shows how to print the copyright notice on all pages but the last instead of just the first page.

```\paper {
oddFooterMarkup = \markup {
\unless #on-last-page-of-part \fill-line {
}
}
}

copyright = "? LilyPond Authors. License: GFDL."
tagline = "? LilyPond Authors.  Documentation placed
under the GNU Free Documentation License
version 1.3."
}
```