Added lume.first() and .last(), updated README.md and tests

README.md

@@ -178,6 +178,20 @@ than a string. Creates and returns a new array of the given slice.
 lume.slice({"a", "b", "c", "d", "e"}, 2, 4) -- Returns {"b", "c", "d"}
 ```
 
+### lume.first(t [, n])
+Returns the first element of an array or nil if the array is empty. If `n` is
+specificed an array of the first `n` elements is returned.
+```lua
+lume.first({"a", "b", "c"}) -- Returns "a"
+```
+
+### lume.last(t [, n])
+Returns the last element of an array or nil if the array is empty. If `n` is
+specificed an array of the last `n` elements is returned.
+```lua
+lume.last({"a", "b", "c"}) -- Returns "c"
+```
+
 ### lume.invert(t)
 Returns a copy of the table where the keys have become the values and the
 values the keys.

lume.lua

@@ -257,6 +257,18 @@ function lume.slice(t, i, j)
 end
 
 
+function lume.first(t, n)
+  if not n then return t[1] end
+  return lume.slice(t, 1, n)
+end
+
+
+function lume.last(t, n)
+  if not n then return t[#t] end
+  return lume.slice(t, -n, -1)
+end
+
+
 function lume.invert(t)
   local rtn = {}
   for k, v in pairs(t) do rtn[v] = k end

test/test_lume.lua

@@ -266,6 +266,22 @@ tests["lume.slice"] = function()
   testeq( lume.slice({"a", "b", "c", "d", "e"}, -3, 900), {"c", "d", "e"} )
 end
 
+-- lume.first
+tests["lume.first"] = function()
+  local t = { "a", "b", "c", "d", "e" }
+  testeq( lume.first(t),    "a"           )
+  testeq( lume.first(t, 1), { "a" }       )
+  testeq( lume.first(t, 2), { "a", "b" }  )  
+end
+
+-- lume.last
+tests["lume.last"] = function()
+  local t = { "a", "b", "c", "d", "e" }
+  testeq( lume.last(t),     "e"           )
+  testeq( lume.last(t, 1),  { "e" }       )
+  testeq( lume.last(t, 2),  { "d", "e" }  )  
+end
+
 -- lume.invert
 tests["lume.invert"] = function()
   testeq( lume.invert({}),                        {}                  )