Regex for unsigned integers. I am using flex

Question

I have tried the code given on this question (?<![-.])\b[0-9]+\b(?!\.[0-9]), but flex shows: Bad Character: <
Bad Character: !
Bad Character: [
...

Always suspect that lookarounds aren't supported when you get an error like that ! — , Jul 07 '15 at 23:29

score 0 · Answer 1 · answered Jul 07 '15 at 21:01

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I'm not familiar with Flex but from a rapid google search, it appears that flex uses < and > characters for match tokens. Try escaping these characters with a back slash and see if that helps.

< → \<

answered Jul 07 '15 at 21:01

Jason L.

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thanks Jason but I have already tried that, in addition it shows `Bad Character: \\` – rneha725 Jul 07 '15 at 21:04
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In some languages like C#, `(?<` has a special function within the context of a regex. In C#s case, it "captures the matched subexpression into a named group", such as `(?< name > subexpression)`. It's possible that the regex implementation of Flex has a similar construct that would make this regex be considered invalid. – Jason L. Jul 07 '15 at 21:22

score 0 · Answer 2 · edited May 23 '17 at 10:26

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Sorry all, but according to this answer flex doesn't support lookahead. I think I should take this question down.

edited May 23 '17 at 10:26

Community

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answered Jul 07 '15 at 21:24

rneha725

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Regex for unsigned integers. I am using flex

2 Answers2