Bugfixes and New Feature

Fixed bugs with invalid dice notation input.  Using `dice:new('3d4+')`
or `dice:new('3d4^1')` before this bugfix should have caused an error,
but did not due to a loophole in the pattern matching that was used.
This has been changed and it will now cause an error when invalid
notation is used.

Fixed bug involving `dice.__concat` metamethod.  When using the concat
operator, if a dice instance `dice.sets < 1` then it would accidentally
overwrite the notation and exclude the sets.  This resulted in the dice
instance being defaulted to `dice.sets = 1`.

Added new method `dice:getNotation()` this returns the raw notation of
all the dice variables. Using this method if your dice instance has any
of the following faces, num_dice, or sets as a negative it will reveal
it in the string.  `Ex. '(-5d-7)x-2'`  The same dice instance used with
the `dice:__tostring()` metamethod will default those negative values to
1.  `Ex. using the same dice instance '1d1'`

dice.lua

@@ -43,8 +43,14 @@ function dice:new(dice_notation, minimum)
   -- If dice_notation is a number, we must convert it into the proper dice string format
   if type(dice_notation) ==  'number' then dice_notation = '1d'..dice_notation end
 
-  local dice_pattern = '[(]?[-]?%d+[d][-]?%d+[+-]?[+-]?%d*[%^]?[+-]?[+-]?%d*[)]?[x]?[-]?%d*'
-	assert(dice_notation == match(dice_notation, dice_pattern), "Dice string incorrectly formatted.") 
+  local dice_pattern = '[(]?[-]?%d+[d][-]?%d+[+-]?[+-]?%d*[%^]?[+-]?[+-]?%d*[)]?[x]?[-]?%d*'  
+	assert(dice_notation == match(dice_notation, dice_pattern), "Dice string incorrectly formatted.")
+
+  local bonus_notation = match(dice_notation, '[d][-]?%d+([+-]?[+-]%d+)')
+  if bonus_notation then assert(bonus_notation == match(bonus_notation, '[+-]+%d+'), "Dice string bonus portion incorrectly formatted.") end
+
+  local reroll_notation = match(dice_notation, '[%^][+-]?[+-]?%d*')	
+  if reroll_notation then assert(reroll_notation == match(reroll_notation, '[%^][+-]+%d+'), "Dice string reroll portion incorrectly formatted.") end
 
   local merged_notation = dice_notation .. (minimum and '['..minimum..']' or '')
 
@@ -81,6 +87,10 @@ function dice.setClassMin(min) dice.class_minimum = min end
 --- Resets the cache for dice instances
 function dice.resetCache() dice._cache = {} end
 
+--- The raw notation including all negatives
+-- @treturn string
+function dice:getNotation() return self.notation end
+
 --- Number of total dice
 -- @treturn int
 function dice:getNum() return self.num end
@@ -224,8 +234,8 @@ function dice:__concat(pluralism_notation)
 
   local new_dice_notation
 
-  if sets > 1 then new_dice_notation = '('..num_dice..'d'..dice_faces..bonus..rerolls..')x'..sets 
-  else new_dice_notation = num_dice..'d'..dice_faces..bonus..rerolls
+  if sets == 1 then new_dice_notation = num_dice..'d'..dice_faces..bonus..rerolls 
+  else new_dice_notation = '('..num_dice..'d'..dice_faces..bonus..rerolls..')x'..sets
   end  
 
 	return dice:new(new_dice_notation, minimum)