tutorial: add missing line to make example build.

1 files changed, 1 insertions, 0 deletions

diff --git a/doc/tutorial.md b/doc/tutorial.md
index 65e7501a04c..b5eba8a113c 100644
--- a/doc/tutorial.md
+++ b/doc/tutorial.md
@@ -2189,6 +2189,7 @@ printable, and that we wanted the implementation of `print` for those
 types to be exactly as it is for `int`, above:
 
 ~~~~
+# trait Printable { fn print(&self); }
 impl Printable for f32 {
     fn print(&self) { println!("{:?}", *self) }
 }