Added explanation of numerical evaluation of color_f and friends.

diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index b65e71e16f50767eb19e2c9db211beb46d60527e..4a29969f1fd33160b7a0cc2e2718ccfd3231b0a6 100644 (file)
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -3507,6 +3507,11 @@ create the symmetric and antisymmetric structure constants @math{d_abc} and
 @math{f_abc} which satisfy @math{@{T_a, T_b@} = 1/3 delta_ab + d_abc T_c}
 and @math{[T_a, T_b] = i f_abc T_c}.
 
+These functions evaluate to their numerical values,
+if you supply numeric indices to them. The index values should be in
+the range from 1 to 8, not from 0 to 7. This departure from usual conventions
+goes along better with the notations used in physical literature.
+
 @cindex @code{color_h()}
 There's an additional function