regex - Inserting a space between a dot and a character using simple search/replace with regular expressions

Question

I want to separate sentences by inserting a space between each period and letter but not between anything else like a dot and a bracket or a dot and a comma.

Consider this:

This is a text.With some dots.Between words.(how lovely).

This probably has some solution in Perl or PHP but what I'm interested in is can it be done in a text editor that supports search/replace based on regexes? The problem is that it would match both the dot and the character and replace will completely obliterate both. In other words, is there a way to match "nothing" between those two characters?

Answer 1

You could use back references in the replace string. Typically it would look something like:

Search regex:

(.)(w)

Replacement pattern (notice the space):

$1 $2

The back references are stand-ins for the corresponding groups.

Alternatively, you could use lookarounds:

(?<=.)(?=w)

This doesn't "capture" the text, it would only match the position between the period and the letter/number (a zero-length string). Replacing it would, essentially, insert some text.

Really, though, it depends on the capabilities of your text editor. Very few text editors have a "complete" regular expression engine built-in. I use TextPad which has its own flavor of regular expression which largely does not support lookarounds (forcing me to use the first approach).