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Subject: Re: [Caml-list] char/line-numbers in error-messages from
 data-structures bulit via ocamllex?


Dear Chet,

With ocamlyacc and menhir, just keep your type "token" unmodified -- no need
to annotate tokens with positions.

Then, if you are using ocamlyacc, the functions in the module Parsing can be
used to extract position information; if you are using menhir, the position
keywords $startpos, $endpos, etc. can be used for this purpose. (See 
Menhir's
documentation for details.) You can then arrange for your semantic 
actions to
decorate your AST with position information.

In Menhir, you can define a parameterized nonterminal symbol to alleviate
the pain of recording positions. For instance:

located(X):
   x = X
     { (x, $startpos, $endpos) }

Thus, if the nonterminal symbol X has a semantic value of type 'a, then
the nonterminal symbol located(X) recognizes the same strings as X, but
has a semantic value of type 'a * Lexing.position * Lexing.position.
If your nonterminal symbols are expression, instruction, etc.,
then you can use located(expr), located(instruction), etc.,
to automatically obtain decorated ASTs.

I hope this helps,

--
François Pottier
francois.pottier@inria.fr
http://gallium.inria.fr/~fpottier/