Difference Between The 2 Statements

[RN1]

Consider the following RegularExpression:

====================
q[^u]
====================

One of the RegEx tutorials I have come across says the following
w.r.t. the above RegEx:

====================
The above RegEx does not mean a 'q' not followed by a 'u'; rather it
means a 'q' followed by a character that is not a 'u'.
====================

Now what's the difference between the 2 statements that I have cited
above?

Thanks,

Ron

 

[Jesse Houwing]

Hello RN1,

Consider the following RegularExpression:

====================
q[^u]
====================
One of the RegEx tutorials I have come across says the following
w.r.t. the above RegEx:

====================
The above RegEx does not mean a 'q' not followed by a 'u'; rather it
means a 'q' followed by a character that is not a 'u'.
====================
Now what's the difference between the 2 statements that I have cited
above?

Thanks,

condider this input:

q

this could be read as a q not followed by a u.

condider

qd

this could be read as a q not followed by a u.

in regex this would be written as:

q(?!u)

The other regex however will never match the first option, because q[^u]
alsways needs to match at least 2 characters, a q and a different character
than u.

 

[Peter Morris]

q followed by anything as long as it is not q == match
q followed by q == no match

 

[Juan T. Llibre]

Also, q followed by nothing = no match