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Go see Half-Nelson

(as seen from the lobby of one of the theaters on Shattuck Ave.)

So. Movies.

First, let me be up front: I am shilling for a friend here. Once I’ve disclosed the full extent of this, I’ll go on to convince you that it doesn’t matter. Ryan Fleck directed this film and co-wrote it with his girlfriend, Anna Boden, who produced it. Ryan’s dad and my dad lived in a Berkeley commune together, and Ryan’s kind of like my fictive cousin. Friend of the family, not terribly close, but still related, but not technically. Communes make things complicated like that.

So when we went to see it at the SF Film Society’s International Film Festival in April, I was totally willing to cheer my head off for whatever the hell he had made, and clap for family’s sake. Luckily, he’s made an insanely good film. Like, easily the best film I’ve seen in two years–and I’m hard to please. It picked up the Fipresci prize there, and from what I can tell just about every critic who’s ever seen it loved it. It got reviewed on Ebert & Roeper, where Roeper and guest critic Kevin Smith couldn’t stop telling the audience to see it. Entertainment Weekly gave it an A, Time Out New York gave it 5/6, and The Onion gave it an A-. Its Rotten Tomato meter is just under 90%.

The short version? This is an amazing film. It opens in a handful of theaters on Friday. If you pass it up, you’re missing out.

Stupid Ruby Tricks: String#to_proc

I was thinking about one of the cool bits of ActiveSupport, Symbol#to_proc, which allows you to do this:

[1, 2, 3].map(&:to_s) #=> ["1", "2", "3"]

That’s useful for sorting, enumerating, mapping, etc. Quite handy, and it saves you the trouble of writing a block to return a single value. I was recently someplace with a fair bit of time to kill and no reading material, and I began to wonder… how does this work?

Magic via one of the few typographic characters I can’t even write

Oh, the ampersand. Curly figure of import. That little pretzely freak is the sin qua non for this entire operation. You can tell, because Array#map acts all angry when you try to just pass it a Symbol:

irb(main):001:0> [1, 2, 3].map(:to_s)
ArgumentError: wrong number of arguments (1 for 0)
        from (irb):1:in `map’
        from (irb):1

The ampersand is how Ruby denotes a block variable.

Let’s try to pass our block in a different way:

my_block = lamdba{ |x| x.to_s }
[1, 2, 3].map(my_block)

Ruby will raise an ArgumentError because it’s trying to pass your block as a regular method parameter, rather than as a block parameter. Let’s try passing it as a block parameter:

[1, 2, 3].map(&my_block) #=> ["1", "2", "3"]

Sweet! It worked!

Now we’ve got a better of idea of what the hell we’re actually doing. When we write map(&:to_s), we’re saying “call the map function and pass it this block.” But a Symbol isn’t a block!

Very true, and what does Ruby try to do when presented with a type mismatch? Coerce! How? Conversion methods! Anything with a to_proc method can be converted to a proc. Our first example can be rewritten as follows:

[1, 2, 3].map(&:to_s.to_proc) #=> ["1", "2", "3"]

This means that anything with a to_proc method can partake of this lovely syntactic sugar.

Pushing the limits for no apparent reason

And now for the inevitable section of any article on programming that I write: taking things too far.

class String
  def to_proc
    eval "Proc.new { |*args| args.first#{self} }"
  end
end

robots = []
robots << { :name => ‘Jeevesotron’,  :type => ‘robo-butler’ }
robots << { :name => ‘Crushmonster’, :type => ‘robo-baby-sitter’ }
robots << { :name => ‘Fluffy’,       :type => ‘doombot’ }

robots.map(&’[:name].upcase’) #=> ["JEEVESOTRON", "CRUSHMONSTER", "FLUFFY"]

It may not be useful, but it sure as hell is fun.