I'm trying to implement a regular expression matcher based on the backtracking approach sketched in Exploring Ruby’s Regular Expression Algorithm. The compiled regex is translated into an array of ...

I'm trying to use a regex to capture tweets containing the substring 👏 at least twice, so I'm using an unsophisticated ^.+ 👏 .+ 👏 .+$. However this doesn't match strings which instead contain, f...

Possessive quantifiers are greedy and refuse backtrack. A regex /.{1,3}+b/ should mean: Match any character except line breaks, 1 to 3 times, as many as possible and don't backtrack. Tthen match th...

I've come up with this regex that finds all words that start with $ and contain _ underscores: \$(\w+)_(\w+) I'm basically searching for variables, like $var_foo etc. How do I replace stuff usin...

I have this regular expression: regex = %r{\A(?<foo> a\g<foo>a | b\g<foo>b | c)\Z}x When I test it against several strings, it appears to be as powerful as a context free gramm...

I am using textmate to edit a file. I would like to remove all the lines not containing a word. Here is an example. apple ipad hp touch pad samsung galaxy tab motorola xoom How can i remove all th...

I've noticed a side effect in Ruby/Oniguruma that is only present in 1 out of 4 seemingly equivalent statements. Why is the variable day defined in 009, but not in 003, 005 or 007? irb(main):001:0...