Question

I got values like

\w{1,2}-\w{1,2}\d{1,4} and \w{1,2}-\w{1,2} \d{1,4}

I transform these values:

AB-CD 1 -> AB-CD1
AB-CD1 -> AB-CD1

I do it using

[ ]{1}[\d]{1} 

and replacing ” ” to “”. This works well.

But now I need to do the following transformation:

AB-CD1 -> AB-CD 1
AB-CD 1 -> AB-CD 1

I tried a look ahead aiming any digit

(?=\d) 

but then I get two spaces if my text already contains one. I need to select the space (or none) between \w and \d – how do I do that?

Answer 1

You can write:

(?<![\d ]) ?(?=\d)

to match an optional space (i.e., either a space or the empty string) position that does not follow a digit or space and does precede a digit.

((?<!...) is a negative lookbehind assertion; see http://www.regular-expressions.info/lookaround.html.)