From: Jim Weirich <jweirich@...>
Date: 2002-08-22T13:00:13+09:00
Subject: Re: blocks and lambdas, or blocks as first-class entities

>>>>> "Rafael" == Rafael Sevilla <Rafael> writes:

    Rafael> [...] What if we made a block a first class entity,
    Rafael> allowing one to assign a block to a variable, and pass a
    Rafael> block as a formal parameter to a method?  This of course
    Rafael> would also mean making a block an object, which in my
    Rafael> opinion is a very powerful idea.

A Proc object is an objectified block.  You can create a proc object
by saying ...

       proc { |args| ... }
or     lambda { |args| ... }
or     Proc.new { |args| ... }

Proc objects can be assigned to variables and passed to functions

    Rafael> So you might have some code that looks like this:

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

    Rafael> tmp_blk = { |a, b| ... }
    Rafael> foo({ |a, b, c| ... }, tmp_blk)
    Rafael> {|a| ... }.execute(b)

Or using procs ...

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

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

Very similar to your proposal, except we add "proc" and use "call"
rather than "execute" to invoke the proc.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)