Mixed solution parsing

lib/unit.rb

@@ -14,10 +14,14 @@
 
 module Unit
   def self.parse(string)
+    #This is a magic gsub to turn separators into @ symbols.
+    #This will break if you expect a negative number after the initial scalar
+    #e.g. 1%-1:-1000
+    string.gsub!(/(?!^)-/, '@')
     tokens = Lexer.new.tokenize(string)
     Parser.new.parse(tokens)
   rescue
-    raise IncompatibleUnitsError
+    raise IncompatibleUnitsError.new("#{string} is not a valid unit string")
   end
 
   def self.from_scalar_and_uom(scalar, uom)

lib/unit/lexer.rb

@@ -66,6 +66,9 @@ def _next_token
       when (text = @ss.scan(/[:]/i))
          action { [:COLON, text] }
 
+      when (text = @ss.scan(/[@]/i))
+         action { [:SEPERATOR, text] }
+
       when (text = @ss.scan(/\b(?:gm|gram)\b/i))
          action { [:MASS_UOM, 'g'] }
 

lib/unit/lexer_definition.rex

@@ -10,10 +10,13 @@ macro
   UNITLESS_UOM \b(?:ea)\b
   EQUIVALENCE_UOM \b(?:meq|eq)\b
   COLON       [:]
+  SEPERATOR [@]
+
 rule
   {BLANK}
   {SCALAR}      { [:SCALAR, BigDecimal.new(text, 10)] }
   {COLON}       { [:COLON, text] }
+  {SEPERATOR}   { [:SEPERATOR, text] }
 
   #Mass
   \b(?:gm|gram)\b    { [:MASS_UOM, 'g'] }