Archive for February, 2010

Problem Solved

Monday, February 22nd, 2010

In the comments section of a recent Atwood post, commentor Paul Jungwirth (search for the name as I can’t find comment permalinks) posted about a problem from a perl mailing list that he would give potential hires. This post is not about the blog post but about the problem from the comments section.

The Problem (from the mailing list):

Consider the following string:

1 2 3 4 5 6 7 8 9 = 2002

The problem is to add any number of addition & multiplication operations wherever you’d like on the left such that in the end you have a valid equation. So for example if it gets you to a solution you can have:

12 * 345 + 6 …

if that works as part of your solution [it's much too big: 4146].
Bearing in mind that multiplication takes higher precedence than addition, what is the solution?

My answer generator can be found here in Erlang. I liked the problem because it is in the vein of Project Euler. The eval/1 is a slightly modified version of this one on TrapExit.

Posted in Geekdom | No Comments »

PHP, cURL, and POST

Friday, February 12th, 2010

While working on a script today that had been working, I couldn’t for the life of me figure out why it was failing. It uses the PHP curl_* functions to make various requests and processes the results. Turns out when you send a POST body with the CURLOPT_POSTFIELDS and a value field begins with an at symbol(@), you have to escape it (\@). The reason is the at symbol is used by curl to denote a file upload path (“@/path/to/upload.file”). So escape the at symbol and you should be back to good with the curling.

Posted in Geekdom, Research, Work | No Comments »

Adding Files To Subversion

Wednesday, February 10th, 2010

Working with symfony, especially when adding to the schema and generating the model, form, and filter classes, it becomes tedious to add each of the new files to your subversion repository. Here’s a succinct line to add all un-versioned files to your repo:

#!/bin/sh
 
svn add `svn st | grep ? | head | awk '{print $2}'`

The key is in the tick-marked section. It takes the output of svn st(atus) and pipes it to grep, selecting only the un-versioned files (denoted by the ?), pipes that to head which outputs the first 10 (by default) lines, and pipes that to awk which prints the second column containing the file path to be added.

But what if you have more than 10 files to add? You can easily pass a -n NUM switch to the head command to increase the number of lines it reads in at a time. I’ll leave it as an exercise to the reader to modify the script to allow a user to pass in what NUM should be.

So when your “svn st” output is filled with un-versioned files, all of which you need, run this little guy and have it done speedily.

Posted in Geekdom, Research, Work | No Comments »

More Erlang+Emacs

Wednesday, February 3rd, 2010

I have found that Distel’s built-in shell launcher wasn’t cutting mustard as I needed to start shells with various flags and didn’t see an easy way to accomplish this using what Distel provided. Digging around the Erlang mailing list, I found an elisp function that allowed me to pass flags to the shell. Place this snippet in your .emacs file after you’ve required erlang and distel:

(defun erl-shell-with-flags (flags)
  "Start an erlang shell with flags"
  (interactive (list (read-string "Flags: ")))
  (set 'inferior-erlang-machine-options (split-string flags))
  (erlang-shell))
 
;; map Ctrl-c Ctrl-z to the new function
(global-set-key "\C-c\C-z" 'erl-shell-with-flags)

Now when you start the erlang shell, a “Flags: ” prompt will be presented. Simply add flags as you would on the command line and the shell will start up. Great for when you need multiple shells with different snames, names, cookies, etc…

Posted in Fun, Geekdom, Research | 1 Comment »