Use .absent? in parser rules

lib/litter/parsing/parser.rb

@@ -26,24 +26,25 @@ def initialize(config)
 
       rule(:newline) { str("\n") }
       rule(:space) { match('\s').repeat(1) }
+      rule(:digit) { match('[0-9]') }
       rule(:date_sep) { str(config.fetch(:date_sep)) }
       rule(:loc_char) { str(config.fetch(:loc_char)) }
       rule(:qty_char) { str(config.fetch(:qty_char)) }
       rule(:tag_char) { str(config.fetch(:tag_char)) }
-      rule(:not_tag) { match( "[^\\n\\#{config.fetch(:tag_char)}]") }
+      rule(:not_tag) { newline.absent? >> tag_char.absent? >> any }
       rule(:not_special) {
-        match("[^\\n\\#{config[:qty_char]}\\#{config[:loc_char]}\\#{config[:tag_char]}]")
+        newline.absent? >> qty_char.absent? >> loc_char.absent? >> tag_char.absent? >> any
       }
 
-      rule(:year) { match('[0-9]').repeat(4,4) }
-      rule(:day_or_month) { match('[0-9]').repeat(1,2) }
+      rule(:year) { digit.repeat(4,4) }
+      rule(:day_or_month) { digit.repeat(1,2) }
       rule(:date) { (year >> date_sep >> day_or_month >> date_sep >> day_or_month).as(:date) }
 
       rule(:location) { space.maybe >> loc_char >> not_tag.repeat(1).as(:location)}
       rule(:date_line) { date >> location.maybe >> newline }
 
       rule(:name) { not_special.repeat(1).as(:name) }
-      rule(:quantity) { qty_char >> match('[0-9]').repeat(1).as(:quantity) }
+      rule(:quantity) { qty_char >> digit.repeat(1).as(:quantity) }
       rule(:tag) { space.maybe >> tag_char >> match('[^\n]').repeat(1).as(:tag) }
       rule(:item) { name >> quantity.maybe >> location.maybe >> tag.maybe }