Lazy regexp is not lazy enough

Rails
1

Consider the string

xyz

x P0 y

x Q1 y

1 Placeholder2 2

abc

and the pattern

<(h\d)>.?Placeholder2.?</\1>

the pattern matches

x P0 y

x Q1 y

1 Placeholder2 2

I want it to match

1 Placeholder2 2

How can I do this? That is, I want to find the nearest

…


surrounding Placeholder2.
2

On Feb 8, 3:46pm, Ralph S. [email protected] wrote:

I want it to match

1 Placeholder2 2

How can I do this? That is, I want to find the nearest

…


surrounding Placeholder2.

Don’t know if/how to bend ruby’s regular expressions to do this but
trying to parse html with regular expressions is doomed to fail
eventually. Use something like nokogiri.

Fred

3

Ralph S. wrote in post #980334:

How can I do this? That is, I want to find the nearest

…


surrounding Placeholder2.

First, I’ll +1 Fred on using Nokogiri for parsing HTML.

But you can modify you regex so any markup ‘<’ characters are excluded
using [^<], as in:

p = /<(h\d)>[^<]+Placeholder2.*?</\1>/
s = “xyz

x P0 y

x Q1 y

1 Placeholder2 2

abc”
p =~ s
=> 33

$1
=> “h1”

Is that what you meant?

  • ff
4

Ralph S. wrote in post #980369:

Fearless, your solution seems to work … but I am clueless as to how
and why it works!

I’m FAR from a regex wizard, but it’s worth noting:
[abc] means match any occurrence of a or b or c
[^abc] means match any character that is NOT a or b or c
ergo
[^<] means match anything that is NOT an open bracket
[^<]+ means match one or more things are are not open brackets

so
/<(h\d)>[^<]+Placeholder2.*?</\1>/

matches an open < followed by an h followed by a digit followed by a
close >, then any number of characters as long as they are NOT <
followed by “Placeholder2” … etc

Of course, this will break as soon as someone adds attributes to the

tag, such as

, which is why we all like Nokogiri. I'm sorry your ISP doesn't agree! :)

5

In terms of Nokogiri and Hpricot …

I develop on a Windows machine and my ISP’s machine is a Linux.

Nokoogiri works great on my development machine. My ISP does not
support Nokogiri on his … unless I am willing to spend the money to
have him install it … which I don’t … and for political reasons, I
can’t move to another ISP.

Hpricot has given me lots and lots of problems …

So I have been reduced to parsing some html myself. I don’t want to do
it … but I gotta.

Fearless, your solution seems to work … but I am clueless as to how
and why it works!