improve slice logic

Author: EvandroLG

src/array/init.lua

@@ -59,14 +59,21 @@ array = {
 
     local output = {}
     local _finish = #obj
+    local _start = 1
+
+    if start >= 0 then
+      _start = start
+    elseif utils.is_nil(finish) and start < 0 then
+      _start = #obj + start + 1
+    end
 
     if (finish and finish >= 0) then
       _finish = finish - 1
     elseif finish and finish < 0 then
       _finish = #obj + finish
     end
 
-    for i = (start or 1), _finish do
+    for i = _start, _finish do
       table.insert(output, obj[i])
     end
 

test.lua

@@ -40,10 +40,10 @@ test('slice', function(a)
     { 'javascript', 'python', 'ruby', 'c' }
   )
 
-  --a.deep_equal(
-    --array.slice({ 'lua', 'javascript', 'python', 'ruby', 'c' }, -2),
-    --{ 'ruby', 'c' }
-  --)
+  a.deep_equal(
+    array.slice({ 'lua', 'javascript', 'python', 'ruby', 'c' }, -2),
+    { 'ruby', 'c' }
+  )
 
   a.deep_equal(
     array.slice({ 'lua', 'javascript', 'python', 'ruby', 'c' }, 2, -2),