From: Paul Brannan <pbrannan@...>
Date: 2008-05-12T23:06:04+09:00
Subject: Re: lambda, ->, haskell, and so on

On Sun, May 11, 2008 at 07:24:07PM +0900, Michael Neumann wrote:
> Evan Phoenix wrote:
> > Not to throw the whole thread into a tizzy again, but why again is:
> >
> >  ->(a,b) { }   # stabby proc
> >
> > better than
> >
> >   def(a,b) { } # anonymous def
> 
> shouldn't that be
> 
>     def(a,b) ... end
> 
> otherwise it introduces again a bit of inconsistency. And then "def" is
> used for methods, not procs. Despite, I like the syntax :)

IMO 'def(a,b) ... end' implies that the code between def..end does not
have access to variables in the outer scope (because this is how def
works currently).

I do like the anonymous def, but not as a replacement for lambda.  (it
should be faster to call an anonymous def than to call a proc/lambda)

Currently we have these kinds of functions:

                      anonymous   closure   default args  checks # args
  def foo(a,b); end       N          N            Y             Y
  ->(a,b) { }             Y          Y            Y             Y
  lambda { }              Y          Y            N             Y
  proc { }                Y          Y            N             N
  Proc.new { }            Y          Y            N             N
  define_method { }       N          Y            N             Y

(I can't remember off the top of my head the difference between proc and
Proc.new -- are they the same in 1.9?)

It would be nice if we could build some consistency into this table so
that explaining the differences between all of these was a matter of
following rules, rather than memorizing which mechanisms work which way.

Paul