rational expression with extended letters

parsers/rational_expression.lark

+?rat    :  power 
+        | union
+        | diff 
+        | word 
+        | concat 
+        | kleene 
+        | kleenep 
+        | par 
+        | tokens 
+        | dot 
+        | optional
+
+?par    : "(" rat ")"
+
+?letter : simple_letter
+        | "\l(" hash ")"
+        | "\l" tuple
+hash    : hashable
+
+simple_letter: LETTER
+
+union               : rat "|" rat
+kleene              : (par | letter | dot) "*"
+kleenep             : (par | letter | dot) "+"
+optional            : (par | letter | dot) "?"
+diff                : rat "-" rat
+dot                 : "."
+power               : rat "{" INT "}" | rat "{" INT"," INT "}"
+word                : letter+
+?concat             : rat+
+?tokens             : empty_word 
+	                | complement 
+	                | shuffle 
+	                | intersection 
+	                | unionf 
+	                | differencef 
+	                | symmetric_difference 
+	                | is_superword 
+	                | is_subword 
+	                | contains
+
+empty_word          : "\e"
+complement          : "\complement" par
+intersection        : "\intersection(" rat "," rat ")"
+unionf              : "\\union(" rat "," rat ")"
+differencef         : "\difference(" rat "," rat ")"
+symmetric_difference: "\symmetric_difference(" rat "," rat ")"
+shuffle             : "\shuffle(" rat "," rat ")"
+is_superword        : "\is_superword(" word ")"
+is_subword          : "\is_subword(" word ")"
+contains            : "\contains(" word ")"
+
+
+%import utils.hashable
+%import utils.tuple
+%import common.LETTER
+%import common.INT
+%import common.WS
+
+%ignore WS
+
+