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Message-ID: <4ECE614D.3040504@gmail.com>
Date: Thu, 24 Nov 2011 10:22:53 -0500
From: bob zhang <bobzhang1988@gmail.com>
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Subject: [Caml-list] Weird behavior of Camlp4 Parser

Hi List,
I have came across a strange behavior of the camlp4 parser, (maybe not
that weird due to my limited knowledge of the parser)
The contrived mini-examples as follows :
module MGram = MakeGram(Lexer) ;;
EXTEND MGram
GLOBAL: m_expr ;
m_expr :
[[ "foo"; f -> print_endline "first"
| "foo" ; "bar"; "baz" -> print_endline "second"]
];
f : [["bar"; "baz" ]]; END;;
MGram.parse_string m_expr (Loc.mk "<string>") "foo bar baz ";;
second (** choose the second branch, maybe the token rule has a higher
priority *)

MGram.Entry.clear m_expr;;
EXTEND MGram
GLOBAL: m_expr ;
m_expr :
[[ "foo"; f -> print_endline "first"
| "foo" ; "bar"; "bax" -> print_endline "second"]
];
f : [["bar"; "baz" ]]; END;;
- : unit = ()
# MGram.parse_string m_expr (Loc.mk "<string>") "foo bar baz ";;
first (** here choose the first branch, but the token rule can consume
one token, I thought this should fail *)

Many Thanks