create sum method

Author: EvandroLG

array.lua

@@ -222,6 +222,18 @@ array = {
     return _memo
   end,
 
+  -- Return the sum of the values in table
+  -- @obj {table}
+  -- @callback {function}
+  -- @returns {number}
+  sum = function(obj)
+    raises_error(array, obj, 'sum')
+
+    return array.reduce(obj, function(memo, value)
+      return memo + value
+    end)
+  end,
+
   -- Return a new table joining all values from the two tables passed by parameter
   -- @obj {table}
   -- @obj2 {table}

test.lua

@@ -146,6 +146,11 @@ test('reduce should concatenate all items', function(a)
   a.equal(result, 'abcde')
 end)
 
+test('sum should return sum of the values in table', function(a)
+  local result = array.sum({10, 20, 30, 40, 50})
+  a.equal(result, 150)
+end)
+
 test('index_of should return correct position of value in the table', function(a)
   a.equal(array.index_of({ 20, 30, 40, 50 }, 40), 3)
 end)