doc: add a note about isl_*_intersect and parametric sets

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>

diff --git a/doc/user.pod b/doc/user.pod
index f769885..afd0f2c 100644 (file)
--- a/doc/user.pod
+++ b/doc/user.pod
@@ -2468,6 +2468,11 @@ the same (number of) parameters.
                __isl_take isl_union_map *umap1,
                __isl_take isl_union_map *umap2);
 
+The second argument to the C<_params> functions needs to be
+a parametric (basic) set.  For the other functions, a parametric set
+for either argument is only allowed if the other argument is
+a parametric set as well.
+
 =item * Union
 
        __isl_give isl_set *isl_basic_set_union(