Long story short, this is the solution I came up with:

find /opt/rubyee/bin/ -type f -name '*' -printf '%f,' | xargs -I '{}' -d ,  sudo ln -s /opt/rubyee/bin/{} /usr/bin/{}

A bit of explanation:

find /opt/rubyee/bin/ -type f -name '*' -printf '%f,'

This command finds all (-name ‘*’) files (-type f) in /opt/rubyee/bin and list their names, separated by comma (-printf ‘%f,’). Then the resulting output is passed to the next command.

xargs -I '{}' -d ,  sudo ln -s /opt/rubyee/bin/{} /usr/bin/{}

It basically splits its input stream by comma (-d ,) and executes “sudo ln“, replacing every occurence of {} in its arguments with actual filename.

The resulting command surely seems scary for a novice Linux admin, who I am. Probably I could utilize -exec parameter of the find, but this worked well enough for me. Also, if I did it manually, it actually would be several times faster. But hey, are we programmers or not? :-)

    function next_step() {
        // note how elegant and self-explanatory this code is.
        var cl = 'step_selected';
        $('.' + cl).removeClass(cl).next().addClass(cl);

        // Also look at previous version of the code,
        // before I remembered about chaining methods.

        // var li = $('.step_selected');
        // li.removeClass('step_selected');
        // li.next().addClass('step_selected');

        // Not as sexy, right? :-)
    }

There I was, minding my own business, trying to solve problems in graph theory and I accidentally made a Sudoku puzzle solver! Isn’t it funny how life turns out sometimes? But that’s just how awesome LINQ is.

Eric Lippert on LINQ

1. ensure that the voter hasn’t voted yet, and, if not,
2. increment the number of votes and
3. add the new voter to the array.

MongoDB’s query and update features allows us to perform all three actions in a single operation. Here’s what that would look like from the shell:

// Assume that story_id and user_id represent real story and user ids.
db.stories.update({_id: story_id, voters: {'$ne': user_id}},
  {'$inc': {votes: 1}, '$push': {voters: user_id}});

What this says is “get me a story with the given id whose voters array does not contain the given user id and, if you find such a story, perform two atomic updates: first, increment votes by 1 and then push the user id onto the voters array.”

This operation highly efficient; it’s also reliable. The one caveat is that, because update operations are “fire and forget,” you won’t get a response from the server. But in most cases, this should be a non-issue.

quote from MongoDB site.

How would you implement this in your regular SQL database?

I have decided to try MongoId first. It seems to be a quite good library. However, it still has gaps in documentation. Today I was finding out how to perform an atomic increment of a field. In SQL world this would like like:

update users set spam_count = spam_count + 1;

Mongo Ruby driver supports this kind of operation, but MongoId doesn’t. So I was trying to get down to the driver. And this is what I couldn’t easily find in the docs. If you’re like me, I’ll save you a couple of hours. Here it is:

# assume we know object id already
User.collection.update({'_id' => '4c05848e45760182b5000001'}, {'$inc' => {'spam_count' => 1}})

def get_current_actions(project_id, status_id = params[:status_id] || DEFAULT_STATUS_ID)
    # implementation goes here
end

The code is saying basically this: “if status_id is not passed explicitly, try to take its value from params array. If it doesn’t contain specified key, then fall back to a constant”. This feature (as almost all the rest of Ruby magic) made avaiable by Ruby’s nature: it is interpreted language. This type of code is totally unusual to guys like me, who come from the world of static typing and compiled languages. But I think I’m gonna get used to it :-)

So, prototype it is. I fired up my Balsamiq for Desktop and in under ten minutes mockups of two pages were ready. This is one of them:

But when I sent them to Elen, I thought that maybe she meant some real code, or HTML stubs in real system, because there was a mockup attached to her original email. Here it is:

According to her, she made it in Paint (duh!). And it took her approximately 30 minutes to make this one, because she had to printscreen some real pages and cut pieces from them. What a tedious work! :-) And it must be a hell to modify such mockup!

When I told her about Balsamiq Mockups, she became very interested and decided to give it a try. Another happy story. Thank you, Peldi :-)

Related posts: Creating UI mockups with Balsamiq

But later at home I was thinking about it and decided that it may not be as hard as it looks. We can divide the task into two subtasks:

• provide a unique color for each user
• use this color when generating markup for an event

The latter subtask was quite easy to implement, I already knew a place where the markup was generated. I was more scared by the former one. If done in “enterprisey” way, it could involve new property in User entity, new configuration screens, database alterations, etc. But there is a solution almost as good as abovementioned and much more simple. Let’s define a function that maps user name to color. md5() is a good candidate :-)

function get_color_by_name($name)
{
    $html_color_string = substr(md5($name), 0, 6);
    return $html_color_string;
}

I also used RGB<=>HSV transformation functions, because I wanted to get lighter colors. Initially I wanted to highlight event’s name with the color, but it turned out that text is not always readable. I decided not to write functions that calculate good contrasting colors and put a small color rectangle instead of highlight. This rectangle is essentially a span with several &nbsp; ‘s as a body.

So, final result looks like this:

Here is complete patch (it has too big lines to look good on this page)