From: Joel VanderWerf <vjoel@...>
Date: 2007-04-08T03:23:52+09:00
Subject: Re: about functional programming

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