Developing Thoughts

So I came across a feature to implement whose description read “X% of the time, do Y”.  I thought for a second, and then wrote:

class Numeric
  def percent_of_the_time
    yield if rand(100) < self
  end
end

This works great: 15.percent_of_the_time {puts "hello, world"}.

(My unit testing friends are probably freaking out over monkey-patching core classes to be nondeterministic.  Good!)

Then I got to wondering: why can’t I do this in Lisp?  In Arc some things are callable which normally aren’t, but that seems a bit too much like magic to me, and I’m not sure it’s easily extensible to this case.

The problem with making something pseudo-English is that you need to put the noun first, and in Lisp the verb always comes first.

The solution is more obvious than I’d thought: use a library like curly-infix, and then just write a normal function.  Thus, in Lisp, it can be as simple as:

{15 percent-of-the-time (format t "hello, world")}

The only gotcha is that this looks suspiciously like a single-dispatch method call, but if you’re using CLOS generic functions, it’s not.