Regular Expression, specific seq

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Hi
how do i match a specific sequence of the 3 Groups below. aB must come before cD and eF. cD must come before eF.
All groups can match more than once, but in the specified order.

Groups:
aB
cD
eF

Should Match:
aBcDeF
aBcDcDeFeF

Should not Match
cDaBeF

I was trying:

regex = new Regex(@"(aB)*\G(cD)*\G(eF)*");

but it matches the Group in any order !

Posted 15-Sep-14 11:47am

Nikolaj jensen

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PIEBALDconsult 15-Sep-14 18:36pm

What about "aBmNcDxYeF" ? If not, then you probably don't want to use \G at least try removing them.

I also notice that although it "matches", it doesn't capture anything, so it's really only matching a empty string.

What about: @"(aB)+(cD)+(eF)+"

Nikolaj jensen 16-Sep-14 5:17am

hmm, i don't think + will do it, since a group is not required to be present, but can be. + means that it has to be there at least once - right `?

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Sergey Alexandrovich Kryukov · Answer 1 · 2014-09-15T15:29:00

Solution 1

Of course it matches the group in any order, because this is how you wrote your regular expression. Here is the idea: add another group by enclosing all three groups in the given order in round brackets and look for the match of this root group.

—SA

Posted 15-Sep-14 15:29pm

Sergey Alexandrovich Kryukov

Comments

Nikolaj jensen 16-Sep-14 5:23am

Hi Sergey,

should i add (aBcDeF) ?
How do i look for a "root" group ?
How do i make sure that e.g. subsgroup cd can be present many times ?

like

aBcDcDcDeF

or
aBaBcDcDeFeF

Sergey Alexandrovich Kryukov 16-Sep-14 9:38am

I don't quite understand. You look for all matches and all groups and consider only the one having all groups inside.
—SA

Nikolaj jensen 16-Sep-14 11:05am

The important thing for me is to understand how to match a specific order/sequence and not any order of the 3 groups.