From: Tim Connor <timocratic@...>
Date: 2008-02-01T04:25:15+09:00
Subject: Gedankenexperiment on method duck type safety

*braces for the flames to follow*

I had a strange idea this morning, namely, how would I merge the idea
of the contractual nature of static type safety, with the flexibility
of duck-typing.  I know, it's a hot button, and I've read various
other threads that come close, but don't quite address it the same
way.

And I am not seriously proposing this as a "good idea" or anything.  I
was just thinking "hmm, is there any way to get ducktype safety,
without manually throwing ParameterErrors in the header of the method
if something fails a responds_to".  Yes, there are times you want more
complex handling if something doesn't quack, but sometimes you do want
to enforce that, and right now it is just a bunch of extra ifs and
unlesses.

And I know this doesn't fit with he already complex enough method
declarations in ruby.  It's just faux ruby style, because that is my
favorite dynamic language. So, without further prevarication, here is
the aforementioned abomination, for either discussion sake, or
pointing and laughing, whichever floats your boat:

def foo(bar.is_? Array, !bar.is_empty?, baz.responds_to :webbed_feet)