Rebuild html.

docs/sphinx_docs/notebooks/Replacing.rst

@@ -2,6 +2,14 @@
 Replacing Functions in the Dictionary
 =====================================
 
+For now, there is no way to define new functions from within the Joy
+language. All functions (and the interpreter) all accept and return a
+dictionary parameter (in addition to the stack and expression) so that
+we can implement e.g. a function that adds new functions to the
+dictionary. However, there's no function that does that. Adding a new
+function to the dictionary is a meta-interpreter action, you have to do
+it in Python, not Joy.
+
 .. code:: ipython2
 
     from notebook_preamble import D, J, V