From: Clemens Hintze <c.hintze@...>
Date: 2000-12-10T23:40:02+09:00
Subject: [ruby-talk:7004] Re: block syntax/def syntax question/suggestion

>>>>> "Phil" == Phil Tomson <ptkwt@user2.teleport.com> writes:

    Phil> Being very new to Ruby (2-3 days) and very familiar with

Then, may I welcome you here? We really appreciate everyone who wants
to give it a try :-)

    Phil> Perl, I tend to prefer { .. } for block delimiters.  From

Yes ... but see below ...

    Phil> what I can tell in Ruby you can use either do .. end or {
    Phil> .. } for blocks.  What if that flexibility was also allowed
    Phil> for method definitions so that you could have:

    Phil> def somemethod { ...  }

    Phil> in addition to the current syntax:

    Phil> def somemethod ...  end

And here is one BIG difference between Ruby and Perl. In Perl the {
... } are merely block delimiters. You are right! And so for Ruby's
usage of { ... }. 

BUT in Ruby a block (let me call it R-BLOCK) is a TOTALLY DIFFERENT
thing as a block in Perl (P-BLOCK). A P-BLOCK only groups statements
in the source and is only used via compilation stage to determine such
groups of statements!

R-BLOCKs, however, constitutes REAL OBJECTS that happen to CONTAIN
code. Only the R-BLOCKs objects are not DIRECTLY accessible like any
other object. You may access them via:

  yield : Calling an associated block
  block_given? : Check if an block is associated
  proc | lambda | Proc.new : Convert a block to a Proc instance
  &var : - In formal parameter list, convert attached block to a Proc
           instance and pass that to 'var'
         - In an actual parameter list, converts a Proc instance back
           to a R-BLOCK object.

Whereby a Proc instance is something similar to Perl's sub reference:

  sub { ... };

To stress it again, that do ... end and { ... } constitutes REAL
objects, that can be dealt with.

Statements like 'def', 'if', 'for', etc. that need only statement
grouping, but not no R-BLOCK objects, will have the different
syntax/convention, that the statement opens the grouping and a
corresponding 'end' will close it.

You see, no easy way to get Perl's or C/C++'s behavior here!

I hope you will anyway find fun with Ruby :-)

(...)

    Phil> Phil

\cle