The first regex does what it’s supposed to do:

- it matches [space]test[dot]

- there’s a capturing group: test

- it replaces the match with the capturing group, so in the end, it removes the initial space and the ending period.

PS. I don’t get what you mean here:

Unknown said:

AHK's regex replacement seems to include all characters into the match that are not explicitly excluded by being in the Regex but outside a capture group.

Hi Jesús Prieto

The expression should indeed capture "test" and the RegExReplace function should return "test". But as you can see from the screenshot of the message box, it returns "This is a littletest Why not?"

It captures "test" and omits from the returned string the characters in the regular expression that were not in the capture group. However, it also returns the entire rest of the string that did not match at all. Or am I misunderstanding the way the function works?

Daniel

Hi Daniel:

Why do you think the RegExReplace function should return just "test"?

I hope it helps if I underline the relevant characters and leave the remaining chars just to see where they are in the original string:

• Original string: This is a little test. Why not?
• Matched substring: This is a little test. Why not?
• Capturing group: This is a little test. Why not?

The replace string is $1, ie, the capturing group:

• Replace string: test

Think about this: The replace string will replace the matched substring in the original string.

• Replaced string: This is a littletest Why not?

Hi Daniel:

Why do you think the RegExReplace function should return just "test"?

I hope it helps if I underline the relevant characters and leave the remaining chars just to see where they are in the original string:

• Original string: This is a little test. Why not?
• Matched substring: This is a little test. Why not?
• Capturing group: This is a little test. Why not?

The replace string is $1, ie, the capturing group:

• Replace string: test

Think about this: The replace string will replace the matched substring in the original string.

• Replaced string: This is a littletest Why not?

Hi Jesús Prieto

you are right and I am wondering how I could misunderstand something so basic... 

Thank you,

Daniel

You’re welcome!

Glad to help you, Daniel.