fixes a typo incorrectly quoting a section wherein the ZeroFunction was first introduced

diff --git a/examples/step-4/step-4.cc b/examples/step-4/step-4.cc
index 7a44af84a28bbf59c0e45a5945cd92c74cf3b841..f4231263d345a559a57eda21711ca890a984c7dc 100644 (file)
--- a/examples/step-4/step-4.cc
+++ b/examples/step-4/step-4.cc
@@ -118,7 +118,7 @@ private:
 // simply be omitted for scalar functions.
 //
 // Function objects are used in lots of places in the library (for example, in
-// step-2 we used a Functions::ZeroFunction instance as an argument to
+// step-3 we used a Functions::ZeroFunction instance as an argument to
 // VectorTools::interpolate_boundary_values) and this is the first tutorial
 // where we define a new class that inherits from Function. Since we only ever
 // call Function::value(), we could get away with just a plain function (and