Added lume.keys() and tests, updated docs

README.md

@@ -185,6 +185,9 @@ values the keys.
 lume.invert({a = "x", b = "y"}) -- returns {x = "a", y = "b"}
 ```
 
+### lume.keys(t)
+Returns an array containing each key of the table.
+
 ### lume.clone(t)
 Returns a shallow copy of the table `t`.
 

lume.lua

@@ -264,6 +264,13 @@ function lume.invert(t)
 end
 
 
+function lume.keys(t)
+  local rtn = {}
+  for k, v in pairs(t) do rtn[#rtn + 1] = k end
+  return rtn
+end
+
+
 function lume.clone(t)
   local rtn = {}
   for k, v in pairs(t) do rtn[k] = v end

test/test_lume.lua

@@ -274,6 +274,16 @@ tests["lume.invert"] = function()
   testeq( lume.invert(lume.invert{a = 1, b = 2}), {a = 1, b = 2}      )
 end
 
+-- lume.keys
+tests["lume.keys"] = function()
+  testeq( lume.keys({}), {} )
+  local t = lume.keys({ aaa = 1, bbb = 2, ccc = 3 }) 
+  table.sort(t)
+  testeq( t, {"aaa", "bbb", "ccc"} ) 
+  local t = lume.keys({ "x", "x", "x" })
+  testeq( t, {1, 2, 3} )
+end
+
 -- lume.clone
 tests["lume.clone"] = function()
   local t = {6, 7, 4, 5}