{alsa,pulse}bar: fallback for mywibox variable; closes #384

[etc/awesome.git] / helpers.lua

diff --git a/helpers.lua b/helpers.lua
index b5b663d8cdc8652f8e87c022a75b7b0512dbc2cd..fb71335f91a25a6a6b995648a91a8e45e2ef2649 100644 (file)
--- a/helpers.lua
+++ b/helpers.lua
@@ -1,7 +1,7 @@
 --[[
 
      Licensed under GNU General Public License v2
-      * (c) 2013, Luke Bonham
+      * (c) 2013, Luca CPZ
 
 --]]
 
@@ -10,6 +10,7 @@ local timer      = require("gears.timer")
 local debug      = require("debug")
 local io         = { lines = io.lines,
                      open  = io.open }
+local pairs      = pairs
 local rawget     = rawget
 local table      = { sort  = table.sort }
 
@@ -179,6 +180,28 @@ function helpers.spairs(t)
     end
 end
 
+-- create the partition of singletons of a given set
+-- example: the trivial partition set of {a, b, c}, is {{a}, {b}, {c}}
+function helpers.trivial_partition_set(set)
+    local ss = {}
+    for _,e in pairs(set) do
+        ss[#ss+1] = {e}
+    end
+    return ss
+end
+
+-- creates the powerset of a given set
+function helpers.powerset(s)
+    if not s then return {} end
+    local t = {{}}
+    for i = 1, #s do
+        for j = 1, #t do
+            t[#t+1] = {s[i],unpack(t[j])}
+        end
+    end
+    return t
+end
+
 -- }}}
 
 return helpers