Adds support for dynamic pair and bgp mask expressions.

1 files changed, 4 insertions, 1 deletions

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 8d8ec35..5027c3e 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -572,7 +572,8 @@ incompatible with each other (that is to prevent you from shooting in the foot).
 	  to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
 
 	<tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
-	  65535. Literals of this type is written as <cf/(1234,5678)/.
+	  65535. Literals of this type are written as <cf/(1234,5678)/. The same syntax can also be
+	  used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/).
 
 	<tag/string/ This is a string of characters. There are no ways to modify strings in
 	  filters. You can pass them between functions, assign them to variables of type <cf/string/, print
@@ -640,6 +641,8 @@ incompatible with each other (that is to prevent you from shooting in the foot).
 	  For example, if <cf>bgp_path</cf> is 4 3 2 1, then:
 	  <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true, but 
 	  <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false.
+	  BGP mask expressions can also contain integer expressions enclosed in parenthesis
+	  and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
 	  There is also old syntax that uses / .. / instead of [= .. =] and ? instead of *.
 	<tag/clist/ 
 	  Community list is similar to set of pairs,