| While continuing to experiment with the arity overloading from http://arclanguage.org/item?id=16771, I quickly got out of hand with trying to add more features and error-handling. (If anyone's interested, I could throw up the ugly mess on my bitbucket.) But after all my effort, it got me thinking. Arc already has a version of arity overloading with optional parameters, so what errors does it see fit to trigger? As it turns out...nothing, really: arc> (def without-optparm (x y) (list x y))
#<procedure: without-optparm>
arc> (without-optparm)
Error: "procedure without-optparm: expects 2 arguments, given 0"
arc> (without-optparm 1)
Error: "procedure without-optparm: expects 2 arguments, given 1: 1"
arc> (without-optparm 1 2)
(1 2)
arc> (without-optparm 1 2 3)
Error: "procedure without-optparm: expects 2 arguments, given 3: 1 2 3"
arc> (def with-optparm (x (o y)) (list x y))
#<procedure:zz>
arc> (with-optparm)
Error: "car: expects argument of type <pair>; given ()"
arc> (with-optparm 1)
(1 nil)
arc> (with-optparm 1 2)
(1 2)
arc> (with-optparm 1 2 3)
(1 2)
arc> (with-optparm 1 2 3 4)
(1 2)
arc> (with-optparm 1 2 3 4 5 6 7 8 9 10)
(1 2)
Now, a look at ac.scm will tell you as much: ac-complex-fn translates fns with optional or destructuring args into a Scheme lambda that takes a single rest parameter. Which means that we even have this: arc> (def with-dsparm (x (y z)) (list x y z))
#<procedure:zz>
arc> (with-dsparm 1 '(2 3) 4 5 6)
(1 2 3)
I'm not really concerned about bugs this can introduce. What I actually find odd is that it's taken me this long to notice. What else would I think "yeah, that should be an error" about, even though I've never actually run into the problem? |
