Added lume.invert()

README.md

@@ -115,6 +115,13 @@ an error is raised,
 lume.reduce({1, 2, 3}, function(a, b) return a + b end) -- Returns 6
 ```
 
+### lume.invert(t)
+Returns a copy of the table where the keys have become the values and the
+values the keys.
+```lua
+lume.invert({a = "x", b = "y"}) -- returns {x = "a", y = "b"}
+```
+
 ### lume.set(t [, retainkeys])
 Returns a copy of the `t` table with all the duplicate values removed. If
 `retainkeys` is true the table is not treated as an array and retains its

lume.lua

@@ -126,6 +126,13 @@ function lume.reduce(t, fn, first)
 end
 
 
+function lume.invert(t)
+  local rtn = {}
+  for k, v in pairs(t) do rtn[v] = k end
+  return rtn
+end
+
+
 function lume.set(t, retainkeys)
   local tmp = {}
   for k, v in pairs(t) do tmp[v] = k end