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Date: -- (:)
From: Xavier Leroy <xavier.leroy@i...>
Subject: Re: [Caml-list] ocamllex -- ambiguous regex
> What happens if there is an ambiguous regexp in ocamllex input?
> [The manual doesn't say]

That's an oversight in the manual; thanks for reporting it.
If several regexps match a prefix of the input, the regexp selected is
- the one that matches the longest prefix (so-called "longest match rule")
- in case of tie on prefix length, the regexp that occurs first in the
  source .mll lexer.

For instance:
   "kwd"      { rule 1 }
 | ['a'-'z']+ { rule 2 }

The input "kwdkwd" will trigger rule 2 (longest match), but "kwd01"
will trigger rule 1 (first rule among the two that have longest match).

- Xavier Leroy

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