From: Markus <markus@...>
Date: 2004-09-25T04:24:45+09:00
Subject: Re: [BUG] 1.8.1 & 2 proc bug


     Well, that didn't take long.  Although I sadly can not read
Japanese, from this:

Thu Oct 30 02:46:35 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>

	* eval.c (proc_invoke): single array value to normal Proc#call
	  (i.e. not via lambda call), should be treated just like yield.
	  [ruby-dev:21726]

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-dev/21726

...it appears that yield was broken and so it was decided to break
Proc#call to match it, rather than fixing yield.  It appears that that 
was done by adding the following:

from eval.c near line 7175:

    pcall = data->flags & BLOCK_LAMBDA ? YIELD_PROC_CALL : 0;
    if (!pcall && RARRAY(args)->len == 1) {
	avalue = Qfalse;
	args = RARRAY(args)->ptr[0];
    }

(NOTE: I do not claim to be C programmer, and this is just is just a
preliminary exploration).

     I will admit, having just spent six months full time getting 14,000
lines of code in ruby 1.8.0 to validate against a legacy code test
suite, including several out of state trips for multi-day meeting to
justify the validation process, etc.  I a tad worried that what I had
thought would be a week or so of re-running the tests on 1.8.1 & 1.8.2
is looking like something that will be much, much worse.

     Ok, not a tad worried.  Near panic maybe?

     I can of course back the change out (hurray for open source!) but
that would mean a fork forever more, or having my successors repatch
each new version for the rest of time--neither of which I care for.  So:

      * Is there anyone who reads Japanese or who is aware of any
        discussion of this point in english that can point out to me if
        I am looking at things incorrectly?
      * Is it too late to argue against this change?
              * It goes against POLS, since 1) adding an argument to an
                argument list can _reduce_ the number of arguments seen
                by the Proc, 2) adding or removing one argument can
                change the class of another argument, 3) it makes it
                impossible (so far as I can see) to write iterators that
                process nested arrays in a reasonable fashion.
              * It breaks a design pattern (head,*rest) with a forty
                year history which is used in a great quantity of
                published literature, including the heritage of lisp,
                prolog, smalltalk, etc.
              * If changed back, anyone wanting the "new" behavior could
                get it by simply placing an "*" before the parameter
                passed in
              * If NOT changed, it is not at all clear how the behavior
                could be cleanly worked around
      * If I am too late to this debate, is there anyway that this could
        be made conditional, e.g. by putting a flag on the Proc, or
        adding a global setting or...?  I would want something that was
        within the ruby code, rather than something that affected the
        compilation of ruby (e.g. a compilation/configuration option)
        because having multiple versions of ruby floating around with
        different semantics is dangerous.

     I am willing to do the work on this, but I will need someone to vet
my C, and could use some guidance as to the best route to proceed.


     -- Markus