I would like to detect the following sequences:
a
aA
aAa
aAaA
...
where a~[a-z] and A~[A-Z], the case alternates and the first letter is always lower-case.
Thanks,
Tom
views:
67answers:
3
A:
Tanascius example would match things like 'Aa' and 'aAA'. I haven't tested this, but should work mostly:
^([a-z][A-Z]?)+$
gnp
2010-04-17 20:44:21
This will also allow `aa`.
Gumbo
2010-04-17 20:47:44
His example won't. Your example on the other hand will match stuff like `aaaBaB`.
Blixt
2010-04-17 20:49:00
How should my regex match Aa? I demand a lower case character in the first position ...
tanascius
2010-04-17 20:59:36
This regex is just incorrect---it matches an arbitrary sequence of lowercase characters at any time, which is exactly contradicted by the specification. Tanascius has the right idea.
Antal S-Z
2010-04-17 23:18:00
+4
A:
The regex that @tanascius gave is fine, and based on that, a shorter one could be:
([a-z][A-Z])*[a-z]?
A major difference is that this one will match the empty string. I wasn't sure from the examples if that was allowed.
JXG
2010-04-18 09:24:24
+1 too: If a zero-length string is valid, this would be the way to go. But I think @tanascius is right, and at least one character is required.
Alan Moore
2010-04-18 09:39:50