Re: [Chicken-janitors] #636: irregex behaves differently with overlapping character sets on some machines

[Chicken Trac]

#636: irregex behaves differently with overlapping character sets on some
machines
-----------------------------+----------------------------------------------
  Reporter:  sjamaan         |       Owner:         
      Type:  defect          |      Status:  new    
  Priority:  critical        |   Milestone:  4.8.0  
 Component:  core libraries  |     Version:  4.7.x  
Resolution:                  |    Keywords:  irregex
-----------------------------+----------------------------------------------

Comment(by sjamaan):

 The bug appears to be in the nfa->dfa conversion, since the NFA resulting
 from this SRE is exactly the same before and after the breaking change.

 I've managed to reduce it further to an even simpler match, which gets
 compiled to this DFA:

 {{{
 #;2> (pp (nfa->dfa (sre->nfa (quote (seq (+ print) white)) ~none)))
 #((#f (#((#\tab . #\newline) (#\space . #\~)) . 1))
   (#f (#((#\tab . #\tab) (#\! . #\~)) . 2) (#\space . 2) (#\newline . 2))
   (#t (#((#\tab . #\tab) (#\! . #\~)) . 2) (#\space . 2) (#\newline . 2)))
 }}}

 It should look something like this (the accepting state should be left
 when encountering a non-whitespace character):

 {{{
 #((#f (#((#\tab . #\newline) (#\space . #\~)) . 1))
   (#f (#((#\space . #\~)) . 2) (#\tab . 2) (#\newline . 2))
   (#t (#((#\! . #\~)) . 1) (#\space . 2) #((#\tab . 2) (#\newline . 2))))
 }}}

 It's most likely in the hairy {{{nfa-join-transitions!}}} procedure. I
 don't understand it anymore so I'll probably just end up rewriting it ;)

-- 
Ticket URL: <http://bugs.call-cc.org/ticket/636#comment:6>
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