From: Chris Carter <cdcarter@...>
Date: 2007-04-08T03:31:58+09:00
Subject: Re: about functional programming

On 4/7/07, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> Rick DeNatale wrote:
> > On 4/6/07, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> >
> >> More generally, though, the only way to pass more than one block to a
> >> method is to turn all but one of the blocks into procs, like this:
> >>
> >> meth_with_two_blocks(proc {...}) { ... }
> >
> > I generally recommend using Kernel#lambda instead of  Kernel#proc the
> > difference is subtle, but unless you want to allow non-local returns
> > from a block lamba is almost always the right choice.
> >
>
> Do you mean Proc.new? IIRC Kernel#proc and Kernel#lambda are aliases.
> Proc.new is the one with non-local returns, at least as of 1.8.6.[1]
>
> There is another reason to not use #proc, which I have yet to resign
> myself to: it is going away in some future ruby, and we will have to
> type two more characters each time we want to use it.
>
>
>
> [1]
>
> def m
>    foo_lambda = lambda do
>      puts "foo_lambda"
>      return
>    end
>
>    foo_proc = proc do
>      puts "foo_proc"
>      return
>    end
>
>    foo_proc_new = Proc.new do
>      puts "foo_proc_new"
>      return # non-local return
>    end
>
>    foo_proc.call
>    foo_lambda.call
>    foo_proc_new.call
>    puts "didn't get here"
> end
>
> m
> puts "done"
>
> __END__
>
> Output:
>
> foo_proc
> foo_lambda
> foo_proc_new
> done
>
> --
>        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
>
>

Also, Proc.new (and proc in 1.9) do not check arguments strictly:
>> mylam = Proc.new {|x,y,z| p 'hi' }
=> #<Proc:0x013fc75c@(irb):3>
>> mylam[1,2,3,4,5,6,7]
"hi"
=> nil
>> mylam[]
"hi"
=> nil
-- 
Chris Carter
concentrationstudios.com
brynmawrcs.com