helpers: powerset and trivial_partition_set

[etc/awesome.git] / helpers.lua

diff --git a/helpers.lua b/helpers.lua
index f32c4ad57bee9d28e9bf434344d151ab0f0c2cf0..ce655761405b9a972b58cda4e0e8552052b1daee 100644 (file)
--- a/helpers.lua
+++ b/helpers.lua
@@ -1,18 +1,15 @@
-
 --[[
-                                                  
-     Licensed under GNU General Public License v2 
-      * (c) 2013, Luke Bonham                     
-                                                  
---]]
 
+     Licensed under GNU General Public License v2
+      * (c) 2013, Luke Bonham
 
-local easy_async = require("awful.spawn").easy_async
+--]]
+
+local spawn = require("awful.spawn")
 local timer      = require("gears.timer")
 local debug      = require("debug")
 local io         = { lines = io.lines,
-                     open  = io.open,
-                     popen = io.popen }
+                     open  = io.open }
 local rawget     = rawget
 local table      = { sort  = table.sort }
 
@@ -108,22 +105,20 @@ end
 
 -- {{{ Pipe operations
 
--- return the full output of an input command (synchronous pipe)
--- @param cmd the input command
--- @return command output (string)
-function helpers.read_pipe(cmd)
-   local f = io.popen(cmd)
-   local output = f:read("*all")
-   f:close()
-   return output
-end
-
 -- run a command and execute a function on its output (asynchronous pipe)
 -- @param cmd the input command
 -- @param callback function to execute on cmd output
 -- @return cmd PID
 function helpers.async(cmd, callback)
-    return easy_async(cmd,
+    return spawn.easy_async(cmd,
+    function (stdout, stderr, reason, exit_code)
+        callback(stdout)
+    end)
+end
+
+-- like above, but call spawn.easy_async with a shell
+function helpers.async_with_shell(cmd, callback)
+    return spawn.easy_async_with_shell(cmd,
     function (stdout, stderr, reason, exit_code)
         callback(stdout)
     end)
@@ -175,6 +170,29 @@ function helpers.spairs(t)
     end
 end
 
+-- create trivial partition of a set. The trivial partition set is the simplest
+-- partition of a set. For e.g., the trivial partition set of {a, b, c}, is
+-- simply {{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