Trying to use a jflap regex in scala

Question

Pls see the following DFA https://i.stack.imgur.com/iH3RM.png

created via JFLAP. When I convert to regex, JFLAP gives:

  p+(q+pq)(pq)*(λ+p)

When I paste it in the Scala REPL :

  scala> val regex = "p+(q+pq)(pq)*(+p)".r
  java.util.regex.PatternSyntaxException: Dangling meta character '+' near index 14
  p+(q+pq)(pq)*(+p)
                ^
      at java.util.regex.Pattern.error(Unknown Source)

I have two simple questions.

Is that the right regex ? Why does it include a λ ?
How do I use it in Scala since the λ doesn't show up correctly when I paste in repl ?

score 1 · Accepted Answer · answered Jun 11 '12 at 21:52

1

In formal regular expression notation + means "or". The regex you want to use is something like:

p|(q|pq)(pq)*p?

answered Jun 11 '12 at 21:52

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Wow thank you. I tried replacing + with |, and below works perfect. scala> val regex = "p|(q|pq)(pq)*(|p)".r regex: scala.util.matching.Regex = p|(q|pq)(pq)*(|p) – k r Jun 11 '12 at 21:55

Trying to use a jflap regex in scala

1 Answers1