From: Christopher Rose <chrisrose.chrisrose@...>
Date: 2011-02-17T06:13:36+09:00
Subject: Treetop - parsing to nil result

Hello All,
please forgive a very novice question on what may be an arcane topic.  I
have a Treetop grammar defined, the 'tt' compiler seems to digest it
without complaint, I get no errors when I create a new parser instance.
I parse a smallish, syntactically correct example input and get a nil
result, like this;

irb(main):178:0> pA = VHDLParser.new
=> #<VHDLParser:0x8b5bc6c @consume_all_input=true>

irb(main):188:0> resA = pA.parse(exA)
=> nil

irb(main):189:0> resA.failure_reason
NoMethodError: undefined method `failure_reason' for nil:NilClass
  from (irb):189
  from :0


The description at treetop.rubyforge.org seems to suggest that if the
parse fails, the methods failure_reason, failure_line, and
failure_column would exist in such a way as to point to and describe the
reason for failure.

Can someone please suggest some other avenues for debugging this?


Thanks -

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