[Cialug] Regex Question

[jim kraai]

1. recent versions of perl, in the last ten years or so, can do this
directly with its more advanced regex
2. if you're working in JavaScript, I think you want XRegExp
3. manually in two steps using an intermediate marker
4. you'll need to use a procedural language to deal with length


On Fri, Oct 12, 2018, 08:31 Todd Walton <tdwalton at gmail.com> wrote:

> I somewhat frequently run into this specific type of problem... Let's say I
> have this text:
>
> group
>     something  -->  blah
>   another   -->           yes
>
> I want to line these up all pretty like. I want there to be, say, four
> spaces at the start of the something and the another lines, then the word,
> then a number of spaces that varies depending on the length of the first
> word, and then -->, a space, and the final word. Like this:
>
> group
>     something --> blah
>     another   --> yes
>
> If your email reader can handle it, I typed those in in fixed width font,
> for visual clarity. The problem is that no regex I've ever seen has any
> facility for length. I could determine that there should be 14 total
> characters before the -->, and then do this:
>
> search: ^\s+([a-z]{9})\s+-->
> replace: \s\s\s\s\1 -->
>
> That would replace the something line. And then I would reduce the digit by
> 1 and add 1 space before the -->. Then repeat. Then repeat. That's what I
> usually do. But I wish I could somehow say "four spaces, then the captured
> backreference, then a number of spaces equal to 10 minus the captured
> backreference's length". I know that's a mental mouthful, but hopefully you
> can see what I'm getting at. One would think that horizontal tabs were
> invented for this very thing, but they don't always line up right,
> especially if the variability in word length is high, and also I don't want
> tab characters in the result.
>
> Y'all ever run into this kind of problem?
>
> --
> Todd
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