* camlp5 parsing question
@ 2009-10-14 15:27 Aaron Bohannon
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From: Aaron Bohannon @ 2009-10-14 15:27 UTC (permalink / raw)
To: caml-list
I don't understand why I am getting certain parse errors after
extending a grammar. For instance, if I extend the original OCaml
grammar with these rules--
expr: LEVEL "simple"
[ [ "`"; "+"; "-" -> <:expr< 1 >> ]
| [ "`"; "+"; "*" -> <:expr< 2 >> ] ];
--then when I try out the syntax, I get:
# ` + - ;;
- : int = 1
# ` + * ;;
Toplevel input:
# ` + * ;;
^^^
Parse error: '+' '-' expected after '`' (in [expr])
If the grammar is being left-factored according to the description in
the documentation (sec. 3.4 of
http://pauillac.inria.fr/~ddr/camlp5/doc/htmlc/grammars.html), I don't
see why these two rules should get in each other's way. Moreover, the
base grammar defined in "pa_o.ml" seems to use rules with similarly
overlapping initial parts without any trouble.
- Aaron
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