and another Re: doc patch

[Ralf Stephan]

Should I subscribe to the dev-list? Here is a correction and
a suggestion in the patch, the latter just a hint what errors
are being made by newbies. If you don't like it, reformulate.

ralf

 
--- ginac.texi.orig	Mon Mar 15 18:47:17 2004
+++ ginac.texi	Thu Jun 10 19:21:26 2004
@@ -4293,7 +4293,7 @@
 
 @example
 @{
-    symbol a("a"), b("b"), c("c");
+    symbol a("a"), b("b"), c("c"), x("x");
     idx i(symbol("i"), 3);
 
     ex e = pow(sin(x) - cos(x), 4);
@@ -4309,6 +4309,34 @@
 @}
 @end example
 
+This is a good place to remind you that symbols are not uniquely identified
+by their string representation but by the C++ variable they were assigned to.
+This means that the first of the following two examples will not output 6 
+but 0:
+
+ at example
+@{
+    ex f(int n) @{ symbol x("x"); return pow(x+1,n); @}
+    ...
+    symbol x("x");
+    ...
+    cout << f(6).degree(x) << endl; // WRONG
+@}
+ at end example
+
+For clarity, efficiency, and modularity, it should have been coded:
+
+ at example
+@{
+    ex f(int n, symbol& x) @{ return pow(x+1,n); @}
+    ...
+    symbol x("x");
+    ...
+    cout << f(6,x).degree(x) << endl; // RIGHT
+@}
+ at end example
+
+
 
 @subsection Polynomial division
 @cindex polynomial division