From: Logan Capaldo <logancapaldo@...>
Date: 2006-03-09T03:29:07+09:00
Subject: Re: type at rubycentral?


On Mar 8, 2006, at 10:08 AM, Sch�le Daniel wrote:

> and one case is missing there
>
> irb(main):169:0> proc{}.arity
> => -1
>
> which means, all paramers are ignored(right?)
>
>

Negative arities indicate the _minimum_ number of args to a proc that  
takes a variable number of args

min args = abs(arity + 1) if arity < 0 otherwise arity


so a proc with no arg speciafication is the same as proc { |*args| }.  
(You just can't get at the argument list)

proc { |a, *b| } will have an arity of -2

abs(-2 + 1) = 1 so it must be passed at least one arg

proc { |a, b, c| } will have an arity of 3

proc { || } will have an artity of zero (contrasted with proc {  } )