Comments on: Haskell Gem: Unwrapping Indented Text

By: David

David — Sun, 08 Nov 2009 03:53:52 +0000

Paul, very cool, thank you for both of your interesting solutions.

Yitz, thanks for the heads up and I like your insane one-liner I tried to write something that non-Haskellers could find interesting, but I do think your approach is totally rad.

By: Yitz

Yitz — Sun, 08 Nov 2009 01:30:36 +0000

Nice post. It was linked on the Haskell reddit: http://www.reddit.com/r/haskell/comments/a14mv/haskell_gem_unwrapping_indented_text/

More comments there.

By: Paul Battley

Paul Battley — Thu, 05 Nov 2009 23:37:16 +0000

There’s a typo in my solution (“” should be ” “ but I’m not sure what you mean by “real lines”. If you mean that you want a pure function that maps lines with indented lines to lines with the indented lines concatenated, then you could do this:

http://gist.github.com/227510

But that’s not how I’d implement it in Ruby by choice!

By: David

David — Thu, 05 Nov 2009 22:52:52 +0000

Paul, I didn’t say it explicitly, but the goal is to create a pure function that unwraps indented lines only, preserving “real lines”.

By: Paul Battley

Paul Battley — Thu, 05 Nov 2009 22:37:06 +0000

In Ruby:

$stdout << $stdin.read.gsub(/\n +/, ""

It does read the entire file into memory first, though.

By: Rudolf O.

Rudolf O. — Thu, 05 Nov 2009 18:40:34 +0000

Okay, I think I figured it out: http://neverfriday.com/temp/unwrap/unwrap.html

Also, I didn’t see that it was just one step as part of something more. I’m justifying my choice to make this a small program with the fact that it would be easy to chain things up on a GNU/Linux system

I mean, you *are* using cat, piping ;p

By: David

David — Thu, 05 Nov 2009 15:31:32 +0000

Andre: awesome, that’s exactly what I was looking for to be able to compare solutions.

Igor: Very cool!

By: Igor

Igor — Thu, 05 Nov 2009 15:12:00 +0000

Ooops, looks like the HTML sanitizer ate my characters So, the part that looks like @in = ; should look like @in = <>;

By: Igor

Igor — Thu, 05 Nov 2009 15:08:53 +0000

There’s a Perl one-liner for ya:

perl -e ’sub unwrap {$one = join(“”, @_); $one =~ s/\n\s+//g; split(“\n”,$one)} @in = ; print join(“\n”,unwrap(@in)),”\n”;’ < header

The basic logic is the same as the Haskell original, but I used a regular expression for the unwrapping part. The unwrap function in there receives a list of strings and returns a list of "unwrapped" strings.

I admit, this "line" is a bit long, but…

By: Andre

Andre — Thu, 05 Nov 2009 14:49:20 +0000

If you insist that unwrap be a function of a list of strings returning a unwrapped list of strings, an impure Lua solution would be:

function unwrap(lines)
local result = {}
for _, line in ipairs(lines) do
if string.match(line, “^%s” then
result[#result] = (result[#result] or “” .. (string.gsub(line, “^%s+”, ” “)
else
table.insert(result, line)
end
end
return result
end