add inet:subnets()

Signed-off-by: Asbjørn Sloth Tønnesen <ast@2e8.dk>

1 files changed, 19 insertions, 0 deletions

diff --git a/README.rst b/README.rst
index 3bbb9c4..799f602 100644
--- a/README.rst
+++ b/README.rst
@@ -83,6 +83,7 @@ Operator          Description
 ``:hostmask()``   generate hostmask as an address
 ``:flip()``       flip the least significant network bit
 ``:bits()``       return the address bits in a table
+``:subnets()``    return the amount of /n subnets
 ================= ======================================
 
 
@@ -397,6 +398,24 @@ Valid values for ``n`` are ``1``, ``2``, ``4``, ``8``, ``16`` or ``32``.
     { 2, 0, 0, 1,  0, 13, 11, 8,   0, 0, 0, 0,  0, 0, 0, 0,
       0, 0, 0, 0,  0,  0,  0, 0,   0, 0, 0, 0,  0, 0, 4, 2 }
 
+
+``foo:subnets(n)``
+~~~~~~~~~~~~~~~~~~
+
+::
+
+  inet('192.0.2.0/24'):subnets(26) -- returns 4
+  inet('192.0.2.0/25'):subnets(26) -- returns 2
+  inet('192.0.2.0/26'):subnets(26) -- returns 1
+  inet('192.0.2.0/27'):subnets(26) -- returns 0.5
+  inet('192.0.2.0/28'):subnets(26) -- returns 0.25
+
+  inet('2001:db8::/48'):subnets(56) -- returns 256
+  inet('2001:db8::/56'):subnets(64) -- returns 256
+  inet('2001:db8::/48'):subnets(64) -- returns 65536
+  inet('2001:db8::/64'):subnets(56) -- returns 0.00390625
+
+
 Sets
 ----