From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-10-05T00:02:04+09:00
Subject: Re: Too Many Ways?

On Monday 04 October 2004 10:12 am, Gavin Sinclair wrote:
> On Tuesday, October 5, 2004, 12:08:42 AM, trans. wrote:
> >> So in an ideal world I'd have
> >>
> >>   def foo(a,b)        # block forbidden, raise exception if you pass one
> >>   def foo(a,b,&c)     # block required, raise exception if it's missing
> >>   def foo(a,b,&c=nil) # block optional
> >>
> >> That syntax would also allow a 'default block':
> >>
> >>   def foo(a,b,&c=proc{|x| $stderr.puts x})
> >
> > This last should be allowed anyway, me thinks too.
>
> That's bad style, IMO.  I'd prefer to read this:
>
>   def foo(a, b, &c=nil)
>     c ||= lambda { |x| ... }
>     ...
>   end

Better:

   c = lambda { |x| ... }
   def foo(a, b, &c=c)
     ...
   end

Why? Well, there seems to be a general aversion to lambdas in method 
arguments. Probably b/c  a) the Kernel#proc method is needed and  b) 
increased bracketing, i.e. cases like:

 def foo(a, b, &c=proc{|x|
   $stderr.puts x
   # and more
   # to do
 }, &d=proc{|x|
   $stdout.puts x
   # and maybe
   # another
 })

But following your preference to its logical conclusion:

   def foo(a=nil, b=nil, &c=nil)
     a ||= "foo"
     b ||= "bar"
     c ||= lambda { |x| ... }
     ...
   end

T.