parser: SLR(1) 
lexesis: lexer.lxs
terminals:
    "A"
    "B"
    "C"
    "D"
precedence:
    left "A" "D"
    nonassoc "B"
    right "C"
start: <start>
grammar:
    <start> ::= <x> <x>    [startrule];
    <x>     ::= "A" <x>    [xA]
              | "B"        [xB]
              ;