From: John Carter <john.carter@...>
Date: 2003-12-02T06:35:18+09:00
Subject: Rite, Block locals and Autovivification

Perl has what may be an evil solution block locals.

Certainly maximal surprise but Does What I Mean....

What does the bit of Perl
  $a{foo}++
do?

Well, you clearly are referring to a hash, so it makes one.

Since foo doesn't have a  sigil, it takes it as a string...
  $a{'foo'}++

Since the element doesn't exists yet, and we're adding one to it, it
"autovivifies" or "magically grants life" to it. Namely 0. Perl chose 0
since that is "What I Mean" when I add one to and uninitialised something.

Now to Ruby...

def each_anime(io)
  io.each do |line|
    next unless line =~ /evangelion|omg|spirited/
    l = line.length # l is just local to block
    map[$1] = line # Autovivifies map as Hash
    count += 1 # Auto vivifies as 0 on first pass, an gives it scope
               # beyond block.
    weight *= 0.2 # Autovivifies as 1

    yield line
  end
  # l is out of scope here
  [count,weight,map] # Visible at function scope as autovivified.
end



John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
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