From: Rafael 'Dido' Sevilla <dido@...>
Date: 2002-08-22T12:37:02+09:00
Subject: blocks and lambdas, or blocks as first-class entities

As I'm a fan of functional languages as well, feeling comfortable with
languages such as OCaml (which seems to be a favorite other language for
many people on this list), I've noticed that Ruby's blocks look
suspiciously like lambda abstractions in functional languages, just with
a very quirky syntax.  They're pretty much used in the same way, as
parameters to functions, although they're far more limited in scope than
a lambda would be in a Scheme or OCaml, and require somewhat special
treatment.  What if we made a block a first class entity, allowing one
to assign a block to a variable, and pass a block as a formal parameter
to a method?  This of course would also mean making a block an object,
which in my opinion is a very powerful idea.  So you might have some
code that looks like this:

def foo(b1, b2)
  b1.execute(a, b, c)
  b2.execute(d, e)
end

tmp_blk = { |a, b| ... }

foo({ |a, b, c| ... }, tmp_blk)

{|a| ... }.execute(b)

The yield builtin keyword would do the same thing as invoking the
execute method on the first (possibly implicitly specified) parameter.

What do you guys think?

-- 
Rafael R. Sevilla <dido at imperium dot ph>	+63(2)8123151
Software Developer, Imperium Technology Inc.	+63(917)4458925