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I am trying to use JFlex to build a parser but encounter a very basic issue. I want to have this token 

[A-Za-z]+_N$ { System.out.println("Noun"); }

and have it recognize "car_N" as a "Noun" and NOT recognize "car_NN". but it does not work, if I use 

[A-Za-z]+_N { System.out.println("Noun"); }

"car_N" get recognize but "car_NN" returns "car_N" as well, this is not what I want.

I wonder anyone here knows how to help?

JFlex and Flex lookahead symbol '$' does not seem to be working

Jonathan Leffler
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Freddy Chua
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1 Answers1

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I think you're misunderstanding the meaning of '$'. As a lookahead, it matches only at the end of a line of text (hard-line break). As such it works perfectly fine. But it cannot differentiate between car_N and car_NN, except for instances of car_N that are at the very end of a line. Maybe you really want a lookahead something like:

[A-Za-z]+_N/[^A-Za-z]
Christopher Manning
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