From: Brian Candler <B.Candler@...>
Date: 2003-07-09T19:36:41+09:00
Subject: Idea: arity as a range

This may have been suggested before, but I wondered if the use of negative
numbers for arity could be simplified using ranges:

def x(a,b,c); end;     method(:x).arity     #=>   3
def x(a,b,c=nil); end; method(:x).arity     #=>   (2..3)
def x(a,b,*c); end;    method(:x).arity     #=>   (2..nil)

The last example shows a range without an upper bound, which would also be
new. To avoid that, 'arity' could return an object instead:

   class Arity
     def initialize(min=0,max=min)
       @min = min
       @max = max
     end
     # backwards compat?
     def to_i
       if @min == @max
         @min
       else
         -@min-1
       end
     end
     def coerce(y)
       return [to_i, y] if y.kind_of?(Numeric)
       raise TypeError
     end

     # methods based on Range
     def min
       @min
     end
     def max
       @max
     end
     def ===(val)
       val >= @min && (@max.nil? || val <= @max)
     end
   end

Just a thought...

Regards,

Brian.