Tutorial: how to create noncommutative symbols?

This seems to be frequently asked:
<http://www.ginac.de/pipermail/ginac-devel/2015-November/002213.html>

Cherry-picked from dfaba64c.

diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index 3db3518ee9a5cdf781b81d44e89e0624d9513eed..93ed619ffc4c87b0e82de5b4fdaed6119d9e930f 100644 (file)
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -3033,6 +3033,8 @@ canonicalize themselves according to rules specified in the implementation
 of the non-commutative classes. The drawback is that to work with other than
 the built-in algebras you have to implement new classes yourself. Both
 symbols and user-defined functions can be specified as being non-commutative.
+For symbols, this is done by subclassing class symbol; for functions,
+by explicitly setting the return type (@pxref{Symbolic functions}).
 
 @cindex @code{return_type()}
 @cindex @code{return_type_tinfo()}