Synopsis Reserve is a conditional Symbol, constraining the set of strings that a symbol may produce.
  • Symbol \ constraint
where a constraint is any character class, a literal or a keyword non-terminal Symbol.
Description The parser will not accept a reserve symbol if the string accepted by it matches exactly with the constraint. For example, [a-z0-9]+ \ "if" will accept all strings of alphanumeric characters, except for the word if.
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