From: Paul Brannan <pbrannan@...>
Date: 2003-11-27T23:52:08+09:00
Subject: arity of methods defined with define_method

Why do I get the following arities:

irb(main):005:0> [pbrannan@zaphod tmp]$ irb
irb(main):001:0> RUBY_VERSION
=> "1.6.8"
irb(main):002:0> class Foo; define_method :foo, proc {}; end
=> #<Proc:0x402629e8>
irb(main):003:0> Foo.instance_method(:foo).arity
=> -135401849
irb(main):004:0>

[pbrannan@zaphod tmp]$ irb-1.8
irb(main):001:0> RUBY_VERSION
=> "1.8.1"
irb(main):002:0> class Foo; define_method :foo, proc {}; end
=> #<Proc:0x00000000@(irb):2>
irb(main):003:0> Foo.instance_method(:foo).arity
=> 1

In the first case I get a completely unexpected arity; I suspect this is
a bug that was fixed in 1.8?

In the second I get an arity of 1, but I can clearly call the method
with 0 or 3 arguments:

irb(main):004:0> Foo.new.foo()
=> nil
irb(main):005:0> Foo.new.foo(1, 2, 3)
=> nil

I would expect that a method that can take any number of arguments would
have an arity of -1.  Why is this not the case with methods defined with
define_method()?

Paul