fact: Definition plus_expr_pregrammar : pregrammar Ascii.ascii := [[[ "expr" ::== "pexpr" || "pexpr" "+" "expr";; "pexpr" ::== "number" || "(" "expr" ")";; "number" ::== [0-9] || [0-9] "number" ]]].
imports: Fiat.Parsers.ContextFreeGrammar.Notations