- corrected an error due to my ignorance WRT diff_param

diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index 2e307ba0130fa6fc0dfbeddeaeee3eaaa8ce6265..e6d2d1a140b9f59cf44ad63b015820763b97adb3 100644 (file)
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -1543,11 +1543,12 @@ static ex cos_diff_method(ex const & x, unsigned diff_param)
 
 @cindex product rule
 The second parameter is obligatory but uninteresting at this point.  It
 
 @cindex product rule
 The second parameter is obligatory but uninteresting at this point.  It

-is used for correct handling of the product rule only.  For Taylor
-expansion, it is enough to know how to differentiate.  But if the
-function you want to implement does have a pole somewhere in the complex
-plane, you need to write another method for Laurent expansion around
-that point.
+specifies which parameter to differentiate in a partial derivative in
+case the function has more than one parameter and its main application
+is for correct handling of the chain rule.  For Taylor expansion, it is
+enough to know how to differentiate.  But if the function you want to
+implement does have a pole somewhere in the complex plane, you need to
+write another method for Laurent expansion around that point.

 
 Now that all the ingrediences for @code{cos} have been set up, we need
 to tell the system about it.  This is done by a macro and we are not
 
 Now that all the ingrediences for @code{cos} have been set up, we need
 to tell the system about it.  This is done by a macro and we are not