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am a little confused by regular expression to convert to NFAs. am actually test using

http://www.regexr.com/

but some of regular expression like

a*+ab

is that mean (a*)+ is that correct ..

also

ab*+bc*

how can i get b*+ or that mean (ab*)+ i do not know how to get it ?

however is the (a*)+ is the same a+ , i think will match the same ?

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From the examples you give, the site you're using appears to be using "+" to mean "or". Other people use "|" for that but both notations are common enough that they can be called standard.

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  • $\begingroup$ so '+' mean in the examples 'or' boolean operator not one or more item of the preceding $\endgroup$ – Yassine Dec 21 '14 at 10:44
  • $\begingroup$ @Yassine Yes, that's what I just wrote. $\endgroup$ – David Richerby Dec 21 '14 at 10:46

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