whiteout - Say 'No' to Whitespace
I recently whipped up a command-line utility / Ruby gem called ‘whiteout’ which removes trailing whitespace from files. As you would imagine, it’s a simple piece of code, but it’s a bit more convenient than the shell script I was using. It also gave me a chance to learn how to cut a gem and how to structure a command-line utility in Ruby. You can use whiteout to remove trailing whitespace from a single file, a directory of files (recursively), or from standard input:Emacs: transpose-lines
The command transpose-lines, bound to C-x C-t by default, is a standard Emacs workhorse. It exchanges the line point is on with the previous line. Because it also moves point down a line we can invoke it repeatedly to “drag” a line down: one two two two two two< one three three three three --> three< --> one --> four --> four four four four< one five five five five five< one < This is particularly handy for reordering lists.Pretty JSON in and out of Ruby
Parallel to Ruby’s p and pp methods for quickly printing and pretty-printing, Ruby’s JSON library offers j and jj methods for quickly printing objects in JSON format: > obj = {"foo"=>"bar", "baz"=>[1, 2, 3]} > p obj {"foo"=>"bar", "baz"=>[1, 2, 3]} > j obj {"foo":"bar","baz":[1,2,3]} > jj obj { "foo": "bar", "baz": [ 1, 2, 3 ] } Definitely handy for investigating those large, deeply-nested objects. I’ve not actually looked, but the implementation of jj is probably just something like…The Five Minute Lisp Environment
Do you want to try Lisp? Do you have a Mac? Do you have $10? Then this is the post for you! (Ok, you don’t need $10 to try Lisp, but this approach is bloody convenient. And it shows off some really cool tools—and no, sadly I’m not making money on any of them.) First we’re going to install the fantastic Homebrew, which is an easy way to install UNIX tools on your Mac.git: Pushing (Only) Some Commits
Occasionally I’ll find myself deploying to Heroku but for one reason or another I’m not ready to roll out all of the commits I have on master. Maybe I’d like to roll out some of the changes, test, and then roll out the rest later. You don’t want to just run a git push heroku master because that would push (and therefore deploy) everything. Instead, use git log to get hash of the commit you want to push up to (and including), and then run:GitX Commit Keyboard Shortcut
It took me way too long to figure this out: from the commit view (⌘2) in GitX you can use ⇧⌘⏎ to commit.Moved to Octopress
Well, no fanfare necessary, I switched to Octopress and moved this blog to Github Pages. I’m enjoying the new setup and planning to actually post again (*gasp*).Decisions are Bullshit
So many new things to say, so many thoughts, so many feelings…I’m not particularly interested in leaving California (70°F as I write this, among other reasons) but I have affairs to settle in Dallas as well as people I’d like to see. Again I’m struck with the feeling that I need to make better use of the time I spend in Dallas. Not only because life is short and I need to always be making the best possible use of the time that I have, but also because of a growing awareness that the sun is setting on my time with that city.Ruby: Implementing progn from Lisp
While hacking on some Ruby code today I started to miss progn from my Common Lisp programming days. If you’re not familiar with progn, it’s a special form which evaluates all of the contained expressions and returns the value of the last one.
Background
The progn construct is more important in the (more-or-less) functional1 programming world than in the imperative world because it allows us to insert multiple expressions where, syntactically, we could otherwise only insert one.
Let’s start with a trivial example:
(if (> x 0)
x
0)If x is greater than zero, return x, else return 0.
But what if we also wanted to output a message whenever x is not greater than 0? We can’t just add our printing line in before (or after) 0 because the compiler knows what’s what based on the positions of the subexpressions in the if expression: it has to be (if test-form then-form [else-form]) 2.
Enter progn:
(if (> x 0)
x
(progn
(print "Returning zero!")
0))Boom! It works. How very exciting. Ok, maybe not. In fact, I called progn a “special form” earlier—which basically means that it’s something which defies the basic evaluation rule of the language—but the truth is it’s probably the least special of the special forms. In fact, implicit progns are all over the place in Lisp: case forms, catch forms, when forms, let forms, but most importantly, function bodies.